911 and ANI can be a bit confusing. First, if you are using analog trunks, the number that will show up at the PSAP will be the number assigned to it by the telco. Old technology.......old results and very little you can do on the UCX to change that (I think).
If you have digital (PRI or SIP) you have options. The way I set my systems up is first to create an outbound route just for 911 and check the box that says Emergency Route. Then you can go into each user and input whatever 10 digit number you want to send out in the Emergency CID field. Then remove any reference to 911 in your regular outbound routes.
This way, whenever someone dials 911, the UCX will match on your emergency route and because it is flagged as an emergency route, will send the number you have in the Emergency CID field. This is my standard setup whenever I have users with remote phones (especially at home). Works like a charm every time.
I have never tried this setup on analog trunks but if that's your situation, give it a try and see if that works.