Currently only the Note 4 and Note Edge support 700Mhz Band 12 Block A for T-Mobile. I won't buy any phone that doesn't support that band since the new T-Mobile cell Towers with 700Mhz Band 12 Block A are less than 1 mile from my home now.
I'm in the same boat. The missing band was the sole reason I didn't get a 2014 flagship. I don't know why nobody can confirm; the suspense is killing me!
I know it should have it based on the Note or whatever, but so should have the Moto X & Xperia Z3c released 5 months ago.