I don't know of ANY alarm Co. that will "move" a line
I know a lots, however 10 years ago not so easy.
Best method is to identify the phone number of a jumper at the carrier Demarcation point, the alarm compnay most certianly knows how to take it from there.
Other than then that we do not install alarm jacks, not our job!!!.
Anyway thats how the alarm panel is setup, call the line then call it right back so the alarm moden answers....nothing to do with the line.
You can have th alarm company choose another method or put it on a fax (line not heavily used) or dedicated line if its an issue.