Endpoint passing callerid info

Hi,
I have a customer who has had a disaster. They have had to relocate and we have had to install a temp insite system. We could not just deploy ip handsets logged back into our MTE as there would be a retraining issue. We dropped in a key system with sip trunk capability and have connected it to mte. I know I should have a separate sip trunk server but I don't. I have it all working but 1 thing. The key system has the ability to pass callerid name and number per extension if defined. The mte will only look at the callerid assigned to the tenant. I have allowed the tenant the ability to change their callerid. I think this setting is more based on the extension in mte. The connection is setup as a sip trunk in mte, and I set the callerid as asreceived. Any ideas?

Thanks,
Chris