Don't believe so, but why shall I buy a new phone to test for them and also limit the areas where I can travel and still have signal?
We also tried his phone at my home with only 1 bar and I am not living in the rural area...
I get it - there's certainly places where every carrier has trouble and no matter what great deals they might offer, if their service is unavailable, it's just not going to work. Case in point - my dad's old home could only get about 2 bars on AT&T and just about everything else was nonexistent.
That being said, I'll say that the Band 12 incompatibilities are not really T-Mobile's fault. They've been adding it to areas since it penetrates buildings better and travels further (they bought this spectrum from Verizon about two years ago). It seems to be optional, as they are also replacing some 2G/EDGE locations to LTE (offering LTE on 3 or 4 different bands in some areas). Apple took their time adding Band 12 to the iPhone, while a handful of Android devices had it sooner - this is a sort of similar to the missing frequencies on the 4S that kept it working at full 3G/4G speeds on some carriers, or that there were multiple iPhone 5 versions, depending on if you were on AT&T/T-Mobile/other GSM carriers or Verizon/Sprint, even though all had a GSM radio and SIM card slot.
I switched to T-Mobile about 2 weeks ago and there are a few areas that my coverage is poorer, and a few areas where my coverage is better. I sort of see it as a whole that
in my case, the savings and features outweigh the few spotty areas. Besides that, I know that my next iPhone will probably remedy this, as I am in a Band 12 area, but for now, my iPhone 6 is "good enough" for my needs.