Just a bit of insight. I live near UMD in Duluth, MN. Sprint's signal is clearly much 'dirtier' with a 1.0 SNR compared to T-Mobile's 20.4 SNR. I don't have a screenshot from the same time, but I get about a 22 to 29 SNR with T. I know that AT&T uses RRU's but I'm not too sure about Sprint or T-Mobile. Also, I didn't even know they had L2500 where I live, but I force checked it on my Samsung S7 (AT&T).
That might be risky, isn't there still Extended LTE non-native roaming as well? The user would have to be 100% sure they are in the correct part of the coverage map that is treated as native roaming before doing this. I think...?
Good article with open mindedness:
Bronwyn Howell; Are three mobile networks necessarily less competitive than four?