I don't get it. If the collect call from A to B is accepted, B pays the cost of the call. In your scenario B instead calls A directly... and B still pays the cost. Where's the savings here?
(And there's a pretty clear downside to this. What if it's an actual emergency from a different phone than the standard. E.g. the only time I can remember answering a collect call, it was my sister calling from a foreign hospital after a serious accident. Trying to call back at a different number wouldn't have been great. I guess you could have a protocol involving multiple collect calls, and hope that there's no record that the first one was rejected.)
(And there's a pretty clear downside to this. What if it's an actual emergency from a different phone than the standard. E.g. the only time I can remember answering a collect call, it was my sister calling from a foreign hospital after a serious accident. Trying to call back at a different number wouldn't have been great. I guess you could have a protocol involving multiple collect calls, and hope that there's no record that the first one was rejected.)