I'm checking out the two following forums as well:
Getting T-Mobile Wifi Calling working on other ROMS/Devices [ 1 2 3 ... Last ]
Other forums read:
[Q] T-Mobile Wi-fi calling on 4.4 Roms (GE and Sense based)
[Q] TMO Wi-Fi Calling for UVMC 6 TW
[Q] CM7 and Wi-Fi Calling?
Wi-Fi calling possible on bell sim card? (Using the T-Mobile Wi-Fi calling with cm7)