Outboung Caller ID

It would be nice to be able to send outbound caller ID number by outbound route.  If there currently is a PRI used in the system caller ID can only be 1 number. If SIP trunks are used they must be dedicated to certain numbers limiting the number of lines that can be used for each outbound number. When more than one business is sharing a system they cannot share trunks. I know it can be done by extension but some users work for more than 1 company.