Not to take this too far off topic (let me know if this would warrant a new thread!) but has T-Mo made any comment as to what it plans to do with Sprint towers, particularly in areas where coverage is sparse? I traveled on I94/90 between Eau Claire and Madison and coverage is *bad*. It looks like not only are they not able to deploy much B12 since just after Eau Claire is US Cellular territory but they have also not done any B71 upgrades in the area (perhaps there was a straggler TV station that had to move and didn't until later?) so it's all B4/66. I know there are Sprint towers in positions where T-Mo has very low to no native coverage and mostly partner coverage (I'm on an MVNO so I dropped to edge at this point, on the interstate) and it *seems* to make sense they'd keep some, but I guess I don't know if there's a rhyme or reason to it? It might be a bit more clear cut thinking about markets like Nebraska where T-Mo has almost no native coverage as opposed to Sprint but it's hard to say I suppose.
All the 600 Mhz sites in my area were already part of a very dense network, so coverage was never an issue. It seems like every 600 Mhz upgrade was for capacity issues since T-Mobile was also deploying the 5x5 block they had in the AWS-3 band.
The X55 modem can do VoNR (Done on T-Mobile with a OnePlus 8). I would expect T-Mobile to add VoNR via software update to all X55 phones once they have SA and VoNR ready on the network side.
They are trying to get two different results with the upgrades. The 600 Mhz upgrade was to get more range from the site to cover fringe areas. The 2500 upgrade is to get faster speeds & capacity in major population areas.