While roaming on my 5X, I have seen signal check display being connected to USCC LTE (with no 1x connection) and then when a text comes in or goes to be sent, 1x pops up so it can take care of business and then it goes away. This does not happen with the Essential. It literally stays locked on LTE and nothing can be done with it except data (no phone calls, nothing).
I was in Tucson for a couple of days lat week. Visiting a relative. I did encounter some Band 41 at times. It is not everywhere, but it looked like it was in progress. I did notice that in areas with only Band 25, it mostly was weak signal strength and very slow. It surely is a sore spot. It does need some major attention and soon.
While I was not familiar with the actual location of the sites, I would suspect that sites without Band 41 might actually be ground mount sites. I just was not able to take time to locate any cell sites and look at them. I would guess that any upgrade to B-41 would cause the ground mounts to become top mounted. Band 26 antennas probably are on the sites if they have band 41 added. It would make sense to place all the antennas and radios at the proper place and then eventually turn on band 26 when they can.
It seemed that the spacing on the sites are worse than normal probably due to flat land and very few tall buildings. They probably need to start adding some mini-macros to cover the areas that were in-between the old 1900 sites that were too widely spaced.
I also visited Tombstone while in the area. Roamed on AT&T LTE and Verizon CDMA voice while there. Sprint was missing. I made a phone call on the Verizon 1x and also used the AT&T LTE. After one week, looking at Sprint.com, I see nothing to indicate that I will be charged for the use on the other networks.