We have a PRI from the carrier and on CUCM it is a SIP Trunk. We have a company that handles after hours calls through of UCCX. We have a Call Redirect to the company's number but they want to see the caller's telephone's number and not our Caller ID.
CUCM v: 12.5.1 SU4
UCCX v: 12.5.1 SU1 ES03
CUCM Trunk: SIP
Call Flow: PRI --> CUCM SIP Trunk --> UCCX --> No Agents Available -->Call Redirect to toll-free number.
If you look at the call manager traces and the number is what you want it to be, that is all you can control. Whether the carrier accepts what you send to them is another matter entirely. Is SIP -> PRI gateway something you manage or something the carrier manages? If you manage it, see what you get in the output of a "debug isdn q931". It is entirely possible that the carrier will override it with you main telephone number.