Here's my multi-point theory on why Sprint isn't roaming on VZW for LTE:
Fewer Sprint phones have B13 than B12, and at the point that you're roaming on another carrier you want that low-band signal, most of which is still B13 on VZW.
VZW charges more for data roaming than AT&T does, and might not even let Sprint do LTE roaming. This is bolstered by the fact that e.g. FreedomPop uses AT&T rather than Verizon as the underlying network for its stuff...they wouldn't use it if it was expensive.
Also, add the PH-1 to the list of unlocked/BYOD phones that likely have the same firmware as the Sprint version, and thus get WiFi calling (though the PH-1 doesn't have Calling Plus; fingers crossed that I get VoLTE).
I've been in a few RF dead zones (yay hotels!) lately but have seen the phone drop down to native eHRPD rather than swap to roaming on e.g. T-Mo band 12, so my guess is that I won't see aggressive roaming to LTE until the VoLTE soft launch, and maybe not even then.
I'll be heading to the UK in a few months and am trying to figure out whether it's worth it to switch off of Open World (this'll be my first time out of the country, so it's not like I'm using CA/MX data anyway) and grabbing a week pass for while I'm there.
Specifically, does anyone know which network Sprint roams on in the UK, and whether it's LTE roaming?
If the roaming situation is less than ideal, I figure I'll keep Open World and swing by an EE or Three store to pick up a local SIM, using my 3-cent-per-MB Open World data to get there. But if I can get solid coverage on LTE, I'll gladly do the week pass thing to save the hassle of finding a SIM.
Pretty sure they can slowly repurpose LTE portion of M-MIMO to 5G nr so that shouldn't be a problem in the very long run. Just like Clear equipment, and those have served their purpose quite well over the last 6 years.
It is disappointing that Sprint does not have a not Massive MIMO 5G option. I assume the price would be significantly less for less robust solution that would allow for both 4G and 5NR. This would allow more places to have 5NR sooner.