Cell, VoLTE and WiFi Calling: Handoff?

[Old Stoneface]

Google's Project Fi claims that, on its network, devices will hand off seamlessly between carriers and Wifi. E.g.: You can have a call in-progress while connected to a TMO tower and switch to WiFi calling without dropping the connection.

Near as I've been able to tell, from end-user reports, it does work.

So what about being on T-Mobile, having a VoLTE and WiFi calling capable device, and roaming between a WiFi-connected call and a TMO tower? Say I initiate a call from my basement, on WiFi, then wander upstairs and outside, where the phone would normally use a nearby TMO tower? Will the call be handed-off? Same going the other way?

 

[Almeuit]

It should.

 

[raino]

AFAIK, the hand-off between WFC and LTE works OK, but not WFC and a lower network.