Sounds like you need a Coverage Answer Group and a Coverage Path
[ol ]
[li]Pick a non-DID extension and assign a bridged-appearance to your IP phones.[/li]
[li]Create the Coverage Answer Group (add cov answer [next or a specific number]). Enter in all the stations that need to ring simultaneously.[/li]
[li]Create the Coverage Path (add cov path [next or a specific number]).[/li]
[li]For the first Cover point, enter "C[number]", where [number] is the answer group you just created. Enter the number of rings you want those phones to ring before moving on to the next point.[/li]
[li]For the second Cover point, enter the non-DID bridged extension. If you don't assign a number of rings to point 2 then the call will ring there indefinitely - or until the caller gets tired. You can assign a 3rd point, such as voicemail, or whatever.[/li]
[li]Pick your Pilot number and create it as a Virtual Station type. Enter the Coverage Path number you just created as Coverage Path 1.[/li]
[/ol]
Call to the Pilot number should ring all the phones in the group. After so many rings, the button on the IP phones should ring.
I hope that helps.