Will the T-Mobile/Sprint JV use this low band spectrum to fill out the areas that they rely on partners (primarly AT&T and Sprint) to provide their coverage?
Virtually all of T-Mobile's recently acquired 700MHz A band spectrum is in large cities (see my post from 11/2013) and Sprint has been reluctant to add towers in rural areas to utilized the 7MHz of low band SMR spectrum that they are using elsewhere for their Spark service.
Sprint's Current Coverage
T-Mobile Coverage (Light Pink indicates Partner Coverage)
T-Mobile has signaled with the FCC that they are concerned about reasonable roaming rates and Sprint is clearly in the same position with Verizon, needing Verizon's coverage to offer true nationwide coverage. On the other side of the coin, T-Mobile indicates that they already cover 96% of the US population, leaving about 12.5 million POPs to be covered with this new low band spectrum.
For both T-Mobile and Sprint a build out in these uncovered areas would reduce their risk of of significant rate increases or roaming service elimination with Verizon and AT&T, but these towers would be much less efficient than towers elsewhere in their collective networks. Obviously they would share the deployment costs and operating cost, but with these towers would have serve a low number of POPS (population)/Tower which is a standard industry metric on capital efficiency for deployed towers.
How would this affect Sprint's recent regional partners?
Sprint Regional Partners
Building out this spectrum would put Sprint in direct competition with these recent formed partners. These regional partners may also participate in the auction acquiring more spectrum. Each of these partners only needs low band spectrum for wide area coverage, and there are ample amounts of mid-band (PCS/AWS) spectrum in these areas for these regional partners to uses as capacity grows.