I have only called in a hand full of times, but every time it is dead and no one is on there...
I know you can not use google voice to call into the bridge - at least not directly... I have a (718) magic jack number (that no longer has service, but i still can log into and forward anywhere I want) that I forwarded to the bridge and used google voice to call the bridge that way... (because of paranoia and wanting to call the bridge with a "failed" ANI) if people would actually use it i could dedicate this number to forward to the bridge...