With the AT&T Inc. (NYSE: T) merger looking uncertain, a deal with the MSOs behind Spectrum Co. LLC has arguably become the most attractive plan for T-Mobile US Inc. .

T-Mobile needs spectrum, and Spectrum Co., owned by Comcast Corp. (Nasdaq: CMCSA, CMCSK), Time Warner Cable Inc. (NYSE: TWC) and Bright House Networks , has some. In a report issued Friday, Sanford C. Bernstein & Co. Inc. analysts Robin Bienenstock and Craig Moffett note that Comcast and TW Cable together hold a 20MHz block of the 1,700/2,100MHz Advanced Wireless Services (AWS) spectrum that covers about 80 percent of the U.S., and it happens to be the kind of capacity that "would drop neatly and easily into T-Mobile's existing towers."

Considering T-Mobile's near-term spectrum issues and the fact that auctions are still well out on the horizon, "a deal with Comcast and Time Warner Cable for spectrum therefore looks appealing and is very likely the principal Plan B. Or, if you will, the new Plan A," the firm notes.

The real Plan A -- merging with AT&T -- has hit a snag with the U.S. Department of Justice . (See DoJ Blocks AT&T/T-Mobile Merger.)

Plan B could help the MSOs as well. "A deal would give the cable industry a neat answer for 4G (their Clearwire adventure has been an utter debacle) and would provide a clear exit from their spectrum holdings in a way that would satisfy the FCC's desire to crack down on spectrum 'warehousing,'" the analysts argue, noting that the MSOs could, in term, help handle the network's backhaul needs. (See Does Cable Have a Wireless Plan B?)

The pooling of spectrum assets with the cable guys would also tide T-Mobile over until the 2014/2015 spectrum auction.

A cable connection with T-Mobile isn't far-fetched based on recent filings that opposed the AT&T/T-Mobile deal or at least sought some strict conditions. Cablevision Systems Corp. (NYSE: CVC), for example, has revealed a strong interest in running wireless services on the T-Mobile network but believes AT&T would make that road difficult, if not impossible. (See Is AT&T Messing Up Cablevision's Mobile Plans?)

Bernstein estimates the value of T-Mobile and SpectrumCo assets to be about $30 billion, with SpectrumCo's spectrum worth just $2.5 billion, or perhaps much less, since it's currently without a network or buyer that can use it.

— Jeff Baumgartner, Site Editor, Light Reading Cable