Calling Party ID: SIP Trunks to ISDN

I have an Asterisk-based SIP carrier that is mapping the SIP FROM phone number into their ISDN PRI Calling Party ID field (removed the “@host” information). It would seem more logical to map the Privacy ID field when trunking, since this field is controlled by the end-user (Block Sending Caller ID, etc). Is this configurable? Thoughts, comments?