Don't forget that the US Government paid AT&T $6.5 billion to deploy B14 FirstNet spectrum. AT&T took advantage of those subsidized tower climbs to upgrade its own infrastructure to 5G-ready, and add all of its spectrum holdings. Smart move.
T-Mobile doesn't have that subsidy, but I agree that any tower they're going to touch from here on out should be fully upgraded, and I think we'll see that with the Sprint "keep" sites for sure, plus anywhere they add NR equipment.
Likewise. Despite my good experiences with T-Mobile, Sprint was definitely better here. T-Mobile now has the scale and revenue to throw the money at the wall like AT&T and Verizon. They really should focus on upgrading every single site to have every single technology available. There's no reason to hold back anymore.
That's part of the reason why AT&T's network shot up to first place in the U.S. according to independent testing. They stopped bs-ing and started throwing money at the problem. They did it in Mexico too and now their network there is second best and only marginally so.