Microsoft may be gaining a powerful set of partners to help Windows 8 become a success — AT&T and Verizon Wireless, who need leverage against Apple’s onerous demands for subsidies for every iPhone the carriers sell.

Computerworld reports that AT&T and Verizon are both eyeing Windows Phone as the smartphone platform they can promote to push back against Apple demands for high subsidies and royalties. (See also “Smartphone Face-Off: seven Phones Put to the Test.”).

Yankee Group analyst Katie Lewis wrote in her blogthat one reason that one reason that carriers including AT&T and Verizon are backing Windows Phone is that

“Mobile operators are sick of taking orders from Apple…iPhones are occupying an increasingly dangerous share of mobile operators’ smartphone sales. In 2011, iPhones represented half of AT&T’s smartphone sales, and now that Verizon has recently voiced a similar shift in sales, the companies’ fears of an Apple takeover are growing stronger.”

Tero Kuittinen, a mobile analyst and vice president of Alekstra, echoed that when he told the new York Times:

“There clearly is a danger now that iPhone is going to get a stranglehold of the U.S. smartphone market, and I don’t think operators are crazy about that.”

The larger the share of the market that Apple owns, the higher the subsidies it can demand from carriers. Those subidies eat into carrier profits and fatten Apple’s bottom line.

You’ll likely be surprised at just how sizable those subsidies are. Computerworld notes:

Apple’s demands for subsidies in order for a carrier to sell an iPhone are legendary. U.S. carriers heavily subsidize all smartphone hardware, primarily to entice new customers to buy a two-year service contract that costs more than $1,700 over that period. the iPhone 4S with 16GB sells unlocked from Apple for $649 (useful on many GSM carriers with a separate contract), but Verizon, AT&T and Sprint sell it for $199.99 with a two-year contract.

Beyond that, Computerworld notes, Apple also gets a portion of the monthly revenue that carriers get from each customer who buys an iPhone, and it’s a hefty cut, as much as $600. and that number is on top of the subsidies for the phone itself.

Given all that, it’s no surprise that AT&T and Verizon would see Windows Phone as a possible savior. Microsoft badly needs Windows Phone to succeed, and it also doesn’t have the same leverage to demand high subsidies and monthly royalties.

Verizon is particularly interested in pushing Windows 8 phones when they hit. Reuters reports that Verizon CFO Fran Shammo hopes to use Windows 8 phones as leverage against Apple. He told the news service:

“We’re really looking at the Windows Phone 8.0 platform because that’s a differentiator. We’re working with Microsoft on it.”

If the carriers truly do get behind Windows Phone, that will be a big turnaround. They are notorious for doing a terrible job of promoting Windows Phone devices at their retail outlets. the phones often aren’t prominently displayed, and the salespeople don’t go out of their way to recommend them.

If Verizon and AT&T do make a concerted effort to push Windows Phone, it may finally breathe life into the struggling operating system. As the release of the Lumia 900 shows, Windows Phone devices are just as good as iPhones and Android phones — but by itself, that’s not enough.

Windows Phone’s Secret Weapon: iPhone Carriers

AT&T’s balance sheet took a huge hit in Q4 2011, as a one-time break-up charge of $4.2 billion paid to T-Mobile for the merger’s failure saw the company report a net loss of $6.7 billion for the quarter versus net income of $1.1 billion posted a year ago. Also contributing to the loss was a significant charge of ~$6.3 billion toward annual adjustments related to pension and post-retirement benefits accounting. Fourth quarter holiday smartphone sales, however, helped the company post 70% growth in postpaid net subscriber adds and 4% growth in revenues to $32.5 billion compared to the year ago quarter. AT&T activated a record 7.6 million Apple iPhones during the quarter and sold more than twice as many Google’s Android smartphones as it had during Q4 2010.

See our complete analysis for AT&T stock here

A record number of iPhone activations during the quarter puts to rest concerns that deteriorating customer service and heightened competition for iPhone customers from Verizon and Sprint may cause AT&T to lose its stranglehold on the high data ARPU generating iPhone subscribers. With the nearest competitor Verizon reporting only 4.3 million iPhone activations for the quarter, it seems AT&T has done really well to retain as well as lure new iPhone customers with higher speeds that only its 4G HSPA+ network can provide on the iPhone.

Near-Term Hit to Margins

However, AT&T has been giving away huge subsidies on the iPhone as well as other smartphones to drive sales. for example, a basic iPhone 4S model costs around$650 for the carriers who then subsidize it heavily to sell for $199. this has caused AT&T’s wireless operating margins to contract hugely to just over 15% this quarter from close to 30% last quarter.

Data ARPU Levels Should Rise in the Long Run

In return for the subsidy, however, AT&T locks in customers in a long-term contract for its postpaid plans. so we expect the subsidies to pay off in the longer run as they ensure a long-term patronage for AT&T’s higher margin postpaid data plans, thereby reducing churn and bringing in steady cash flows. Smartphone users are typically heavy data users as well, which means that the average revenues generated per user will also increase. AT&T’s postpaid data ARPU increased around 15% over the year-ago quarter, and we expect it to continue to increase over the coming years.

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Last quarter, AT&T had posted only a third of Verizon’s postpaid net adds although it managed to add more number of total connections. this quarter, however, a record number of iPhone activations has helped the company post much better number of postpaid net adds, at about 60% of Verizon’s. While increasing the total subscriber base is essential for a carrier, having a greater postpaid mix among the added customers is even more crucial for the long-term value that each contractual postpaid subscriber brings to the carrier’s business.

It therefore augurs well that AT&T has been trying to improve its data speeds by expanding its LTE network into new markets and bringing out more LTE phones this year. AT&T showed a long list of LTE capable phones at the recently concluded CES 2012, so the huge capital expenditures that the company has incurred in building out its high-speed network should start to pay off soon. (see AT&T Makes Big LTE Push at CES 2012)

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AT&T Stock Slips But iPhone Sales Pumping It Back Up