With regard to the MWI stutter tone: correct, the stutter tone is controlled by the carrier that is provisioned on the OBi device. So, if it's PhonePower, then you are getting a MWI from them, not from Google Voice, and it means you have a message waiting on your PP number, not on GV. You can't indirectly have one phone company's MWI appear on another phone company's service.