Another thing I don't understand is why I can call the number from my cell and it rings my friends phone. When I call it from a landline phone I get a "your call cannot be completed as dialed" message.
each contact or person you called or received a call from with GV will have a unique telephone number from google assigned to it..
these numbers are shared amongst all of the GV subscribers..
so for example someone texts you google will forward the text from NPA-NXX-XXX1 calls to this number from ANY number that is associated as a forwarding number on your GV account will be sent to that person with your GV number as the caller ID.. sort of like a shortcut instead of having to call into your GV number and press 2 to place a call, or using click to call, or an app...
if someone texted my GV number i could end up with the same NPA-NXX-XXX1 number, but when I called that number from one of the numbers associated with my GV number i would reach someone different than you would..
calling from a number that is not linked with a GV account would result in whatever error recording that GV chooses to put up on the line... but even the CBCAD calls would probably be supervised calls...