Have you tried using call transfer instead of redirect? You could put the IVR ext in a partition that the phones reach, while the MeetMe ext would be in a partition that only the IVR can reach.
For example:
phone CSS contains partitionA (not partitionB)
IVR CSS contains partitionB (not partitionA)
- phone dials 1000 that matches 1000/partitionA (IVR ext)
- IVR answers call collects DTMF
- IVR via call transfer dials 1000 that matches 1000/partitionB (MeetMe ext)
-steve