In actuallity, you can set up a voice PRI back to back between two routers. The original poster mentioned that he had MFT-T1 cards so I am assuming he has this module in a 26/36/28/3800 with appropriate DSP resources.
If you want to pass voice calls, you will need to have DSP's in your router whehter they reside in a Network Module, AIM module, or directly on the motherboard on the newer rotuers.
At any rate, with the appropriate hardware and cabling, what you will need to do is configure a pri group under your t1 controller i.e
controller T1 1/0
pri-group timeslots 1-24
you will then get a resulting serial interface in your configuration which lets you configure the parameters of the d-channel.
When you are in a back to back situation, you want one side to simulate the network, so on one of the routers add the following command under the serial interface
int serial 0/0:23
isdn protocol-emulate network
After that, it is simply a matter of setting up your dial-peers approriately to route calls to the pri.
There are configuration examples on cisco.com to help you with that.
