I played with call forwarding on the Extend Home last evening using *72. I discovered that it disables incoming calls to the extension but does not successfully forward calls to either of my test numbers (first is a second Republic phone and the other is my Ooma home phone.) Incoming calls to the smartphone are unaffected, and *73 cancels the unsuccessful forwarding.
While the ATA supports call forwarding, we do not as a service. You can use the phone to voicemail forward but that is it. We have not added a new forwarding function to our service.