So here’s my issue. I have two PBX’s SITE A and SITE B.
When one employee in SITE A Calls another Employee in Site B it works fine. But when Employee in Site B has their find me follow me turned on the call to the Find Me/Follow Me destination fails. In this case the destination is a cellphone. If an employee in site b calls the same employee in site B the find me follow me works fine.
The idea is to encode the external CallerID of the dialing extension in a custom header, and then extract it again on the pstn leg of the call. The linked post uses IAX, but the same could be done with SIP as well.