Customer has a SV 9100 at the main office. There are 3 other locations she has as well. The MAIN thing is that Caller ID on outgoing calls form ALL locations to show the number as it is now. She wants to integrate all stores to the main. Right now each store is independent with there own phone numbers. 2 locations can not port the numbers due to the Rate Exchange. Programming needed can be done to connect all stores but Caller ID is the problem. Right now all analog trunks but this can be changed if I knew what to use.

Suggestions?

SIP trunks allows you to specify the CID by trunk or by extension. Analog trunk CID is controlled by the CO. I'd look into SIP trunks.

Use SV9100 at all locations and integrate them with Netlink.
Then you're able to seize CO lines from main Office from the 3 other locations.
And incoming CO lines can be answered from the other locations, or the same IRG, CAP, VE or dept. grp. that everyone share.