I rarely see B71 or B12. T-Mobile's network is very dense in Houston for me to see those bands. With Sprint, I used to see B26 very often outdoors when I was within the city limits.
Only time I see Band 12/71 is when I'm in East or South Texas. Both Sprint and T-Mobile have terrible tower spacing outside of major interstate corridors. US-59 in East Texas and South Texas has a few noticeable gaps in service, even though coverage maps don't show them.