You can use the E&M card on the AV6 card to interface the PBX, if you have E&M support on the PBX. Otherwise you can run ISDN QSIG or other proprietary signalling (check for the ones supported by Cisco) on the DVM-T1 module to interface the PBX.
Sankar Nair
UC Solutions Architect
Pacific Northwest | CDW
CCIE Collaboration #17135 Emeritus