I was using a Plantronics Focus + BT600 along with Plantronics Hub.
I've upgraded to the Focus 2 + BT700. If I use the Hub, I can answer calls in my softphone (something called HiHi Connect / Communicator.exe) by pressing the Call button on the side of the headset. However, if I change to the Poly Hub, this no longer works.
I note that my softphone app has extensions in it for Plantronics Web API Client v3.4 and Plantronics Add-in v1.0.
Why not keep using the Hub? Because I'm troubleshooting a problem - a few times each day the headset seems to disconnect from the PC - sometimes for a few seconds, sometimes longer, then reconnects. Often seems to happen at the end of a call. I'm sitting less than 0.5m from the BT700,so it's not a distance thing. The BT700 is plugged into the PC USB 3.0 port via a plain 2m USB 3.0 extension cable (not a multiway socket).