I have more questions here than answers. I too, have to ask how you would receive any calls if the pilot number(s) are blocked from being accessible from the PSTN.

Back in the days of REAL telcos, they offered make busy circuits where you could throw a switch and mark an entire trunk group busy, regardless of the number of trunks. I seriously doubt that you'll find a service provider willing to do this now.

We used to configure relays that were controlled by a single button on the receptionist's 1A2 phone. When pressed, these relays would be activated and placed a short on all of the trunks.

Of course, these tricks were performed on traditional loop- or ground-start copper lines. Since the original question doesn't provide enough information, it's hard to provide an answer except to speculate.

Ed Vaughn, MBSWWYPBX