I'm still new to the VWIC-1MFT-T1, but I understand my customer can order a combo T1 from ITC DeltaCom (US Telco) where I can get 6 channels voice (configured as H.323 for Callmanager) and 8 channels data (512k Frame Relay) and split them out inside the 2800 ISR with the MFT card.
Another engineer suggested I needed the WVIC-2MFT-T1-DI but I thought that was only if I had an older PBX and wanted to provide a PRI to that (according to the CCO docs on DI (Drop/Insert).
-jason