The BToE feature for VVX phones only works with the Skype for Business clients, it will not function with the Microsoft Teams clients. Microsoft has chose a different route for the Better Together path between IP handsets and Teams clients, but has not release details on how it will work.
When this is available it will be included in the native Teams Andriod phone client though, which is not applicable to the VVX platform. The newly announced Poly CCX phone line will be running this Microsoft client and thus receive whatever Better Together functionality Microsoft releases.
- Jeff Schertz - Microsoft Solutions Architect [Blog]