Antonio,
Last I knew, the CMS did not allow IP-to-IP routing directly, only through GK process. Quintum had talked about putting this feature in as they do have a separate unit, call relay, that does ip-to-ip routing, but I do not know if they have put this in the CMS yet.
You could, however, use 2 T1 ports, connect them back-to-back, send an incoming IP call out T1-a and come back in on T1-b and then go back out IP, but this will give you double compression/decompression and could affect the quality of the call.