So... my read is Dish sells the spectrum, but uses what they already built (most large metro areas), perhaps shared with AT&T, and they use AT&T for coverage in other areas. The still sell and market the Boost service. Is that not correct?
AT&T is acquiring 20 MHz of the 600 MHz n71 spectrum, which Dish has deployed throughout the country. As well as 30 MHz of 3.45 GHz n77 DoD, which they have not deployed in any meaningful way, if at all.
Under a roaming agreement Boost could roam on to n71 once AT&T takes it over. That's assuming AT&T keeps it and doesn't do a spectrum swap with T-Mobile. It could go either way if AT&T keeps it or not, I think they do keep it, but only time will tell. Maybe they'll wait to deploy it until they are ready for 4.9 so they do one tower climb. Which actually would be the smart thing, since I would think the government will pay for all costs associated with 4.9.
For 3.45, on sites where AT&T already has it deployed, it may just take a software upgrade to take advantage of the former Dish spectrum. And yes, Boost could roam on to that as well.
The rest of their deployed native network is AWS n70 and n66 and n29 700 MHz supplemental downlink. And that's it. n71 was really the backbone of their network and now that's gone. There might be some pockets around the country where n48 is live, if there is it would be very minimal. They have not deployed their c-band or mmWave assets at all.
My own personal speculation:
I'm going to say T-Mobile and Verizon go after the AWS spectrum. I think it may make more sense for T-Mobile, but they've already spent a lot a money in a short period of time with US Cellular and the small fiber companies they are taking over. Once the native Boost network is fully dismantled, any spectrum that is acquired by Verizon will no longer be able to be accessed by current Boost subscribers unless there is a special agreement in place. If T-Mobile gets anything, there is a chance current Boost subscribers will get access.
