Route phone calls through USB headset?

I've been successful at routing both speaker and microphone audio through a USB headset on my OPO. In fact with Skype and 2 other VOIP applications it's just plug and play. It works with no special effort. But with regular phone calls, the phone completely ignores the USB headset.

Has anyone found a way to route phone calls through a USB headset?

Running 12.1, Temasek's unofficial ROM.