Carol,
I am unsure of your problem here. If the call comes from IP to the DX, as long as the match is correct (and the line is active), the call will be sent out the TCRG group. If HND is not correct or the line is down, the DX will not re-route the call, that is up to the orig device to do so.
If you need more assistance on this, please contact me directly at mike_voip@hotmail.com