Quick validation test, to make sure all is as carrier says:
On a phone at main site change CALLING PARTY NUMBER to one of their local main site numbers but not the main one. Call your cell...do you see programmed number? If so, carrier is allowing you to send CPN.
Program that phone with CPN for remote site, try again...does it show remote number? If yes, everything should be in place and now we need to troubleshoot what's wrong at either remote or main.
By the way, 911 calls generally need to leave from the individual local lines at each site to get emergency services to get the right address. This is a function of the ASSOCIATED EXTENSION/EMERGENCY EXTENSION of each phone. Be sure the number in here accesses a local trunk group. PLEASE be sure to have someone test 911 at each site...I usually dial 911 and say "This is not an emergency. I amt testing this phone. Do you show me at <address>?".