Above should be a link to t-mobile expect growth in 2017. You can also Google the leaked investor map for end of 2017.
Over at reddit, the reason is revealed, which is a roaming agreement with US cellular. It comes online, once us cellular turns on volte market by market, Midwest expected to be first.
What I wonder is, volte roaming is same as data roaming in practice, so how about in roaming via republic wireless? Will, perhaps us cellular roaming allow data, will it be invisible to phone?