Sharing PSTN lines from two linked (SIP trunk) servers.

Here is my setup:

trixbox CE 2.6.1.0 linked (SIP trunk) with a asterisk based appliance server (which basicly works like trixbox).
Phones are mostly polycom 330.

The trunk is working really good. Extension 2XX are in one location (A) and 3XX in an other one (B). If I dial 303 from a phone in location A, the call is forwarded correctly and the phone 303 rings and can anwser (sound is good both ways).

Local calling area for A: 444
Local calling area for B: 555

If someone in location B dials 1-444-XXX-XXXX or 444-XXX-XXXX, I created a outbound route that uses the sip trunk between A and B to send the call (the 1 for long distance is trunkated). Right now the server A receives it and I guess it thinks it's an extension giving the user an error message "Invalid extension".

What I want to do is:
If someone in location B dials 1-444-XXX-XXXX or 444-XXX-XXXX, I want to send it to A through the sip trunk and use one of the PSTN lines (analog lines connected through FXO) to call the local number. Basicly I need to tell the server A: If it comes from TRUNK_SIP_B and it has format 444-XXX-XXXX, use PSTN lines to dial.

How do I do that?

thanks