Okay, so we know it's possible (My Reseller Tech with Installer program and I) to do a 3-way direct dial system. System A is a 200 dial plan 1000, System B is a 50 dial plan 2000 and System C is a 50 with dial plan 3000. So far, we've been able to get B and C to dial 1023 and get 1023 on A. However, I cannot dial 3000 to C or 2000 to B from A, B or C without dialing the cabinet number. My tech is banging his head trying to figure out what's going on with F341 and F342 that's giving us fits. A1023 dialing 2000 gets Invalid Extension. A1023 dialing 3000 gets Mailbox Not Found, same with 2000 dialing 3000, and vice-versa. Any hints on what's being done wrong?

You need to make sure that the extensions are unassigned in all of the other cabinets. I find it easier to make site A 1100, B 1200 and C 1300. Since a 1000 dial plan will have a 3000 guest mailbox plan those numbers will need to be unassigned on the 1000 system since looks at the local system first. Hope this helps