Cooter,
This is what I recommend, (and it's clever too!)
So most of these phone system hardware are manufactured by overseas companies with multiple US offices. Whatever type of system you're installing, why don't you go out to their website and pull down their contact info for both overseas and different US offices. That way when you hear the greeting: "Hello, and thank you for calling Jim Bob's Telecom...." You know you hit the right mark.
There is no way around 911, but when your testing the route path, test with 611 first, second and third - however many times it takes to get it right and when you hit it on the nail (ouch) then repeat just the last process (the one that worked) with 911 and start the conversation with "TEST CALL" so the disbatch person dosen't start sending help. Be sure to verify your physical address as well as the caller ID to make sure it's a DID right back to your office. Sometimes if not configured correctly it will display the telco's BTN that can't be dialed and is of no use in locating you.