T-Mobile is committed to blocking Verizon's proposed purchase of AWS spectrum from various cable companies. Verizon recently offered to sell all of its block A and B 700MHz spectrum in exchange for FCC approval of its AWS deal. However, T-Mobile USA CEO Philip Humm personally met with senior FCC officials last week to insist that the sale would not be enough to mitigate any negative effects that the AWS deal would create.
T-Mobile urged the FCC to block the deal, saying that Verizon has not been using its existing AWS spectrum, which it has been sitting on for the past six years. To transfer more AWS spectrum to Verizon would not make sense or be in the public's best interest.
T-Mobile also has plans to build out its own LTE network next year on AWS spectrum. Handing such a large chunk of AWS spectrum from the cable companies to Verizon would harm competitors also wanting to deploy LTE.
Furthermore, the block A and B 700MHz specturm that Verizon is ready to dump has certain issues. For instance, it still lacks a national footprint and faces interference from adjacent high-powered broadcasters and also lacks equipment and interoperability with the rest of the 700MHz band.