Added the "M". I'll let you know if it doesn't work.
Also I played around with the trunk settings and it does roll over to sp2 if both lines are taken. I tried making a an outbound call with 2 lines active. Anytime I tried to call into my gv#, the users were not aware of a call waiting and they did not hear a beep. The phone did ring on the callers side. Is there a setting for this too?