Well, Mike, I don't think you really need to strip IP from the caller id to solve your problem. If I understand right, the problem is with callback ony - you want phones not to callback directly to the xxxxxx@<gateway ip>, but to xxxxxx, so that number will pass through Call Routing Table..

For that you can use the "*@<gateway ip>"-like rule in Call Routing table.
Add a rule (one or more) with pattern=*@<gateway ip>, with the other datails you need.

I.e. if you have a rule 021*, calltype=ISDN, etc, add another rule like 021*@, calltype=ISDN, etc.

Best regards,

P.S. If this doesn't help, I would need the SIP and Call manager logs from Quadro, containing one such callback attempt, and SIP trace log from the Snom for the same call.