Is T-Mobile WiFi Calling available on Google Play Edition HTC One?

I'm currently a Verizon Wireless subscriber, but am looking to switch carriers soon in order to get on a plan that better suits me. I'm giving T-Mobile a serious look because of their "unlimited everything" plan that lets me separate my phone's cost from the plan.

My main concern, however, is T-Mobile's coverage. I've been spoiled with VZW's network... it's great. T-Mobile's WiFi Calling feature could alleviate most of my coverage concerns, but I'm still confused about what devices it's available for. T-Mobile promotes the fact that you can "bring your own device" to their network. Do I need to buy a T-Mobile branded phone in order to make it work or can I buy an unlocked HTC One from the Google Play Store, pop in a T-Mobile SIM and make use of WiFi calling?