IANAL (I Am Not A Lawyer) but here is my understanding. Typically states do not disallow out of state DID's to be used. On top of that Federal law states that 911 calls cannot be blocked. You are required to do your best to deliver the call to the correct Public Safety Access Point, but in any case deliver the call to a PSAP.
So that can create a conundrum on how to direct 911 calls to the proper PSAP to handle the emergency. There's a few companies that can help you with this and more than a couple of consultants that can help point you in the right direction on which way to go. Start with your business partner and see what they recommend, take that with slightly more than a grain of salt and then do more research on your own via DevConnect, google, and asking around some more. The more you know the more pointed questions you can ask.
As for companies supplying services there is Conveyant, RedSky911, West Corporation, and a few other players out there. Their websites can provide a slew of information, but remember that they are also trying to sell a product to you. Some of them work better than others depending on the current configuration of your phone system. Avaya also has some pretty good information on configuring 911 services on the support website. And read up on Mark Fletcher's informative posts to be found all over the web. Fletch is a great source for information on the subject.
Good luck. You can check out the specific laws by going to
and doing some further surfing for the state you need. If it's just Illinois you need then google Illinois 911 law and you will get a bunch of results since they do have a pretty comprehensive set of state requirements for 911. Also, remember that some areas, such as the City of Chicago, can have further, more stringent, requirements too.
