I signed up with Phone Power on the weekend, and I can confirm that you can enter any phone number you wish in the sign up process. (does not have to be your google voice number)
It then shows that phone number and unknown name. But then I made the mistake of clicking on the CNAM name and confirming YES show my name in the phone power settings. At that point it then starting showing only my name and "Long Distance" as the phone number. When I turned it off, it then said "Anonymous" I had to unplug the OBI and reboot before it went back to the number and unknown name.