What I meant was can I plug the RDTU's T into a fxs channel bank in order to have 24 additional analog stations?

I don't need something like an Adtran. I'm using a Digium quad-port-T1-interface in the Asterisk PC - and only using 2 ports, so I can configure the unused ports however I like so it would be nice if I could still utilize the RDTU (which is no longer used) for voicemail.