While I was product manager at Comdial we had a solution as far back as the mid nineties!
Many of you may not remember, in addition to dialing a "9" to get an outside line you could also dial an "8" for long distance in a hotel/motel environment. Businesses would dial the digit "8" for WATS or FX lines.
We used ARS patterns to insure an E911 call would get out!
If you dialed 911 with no digits to follow you were sent to an "insert digit pattern" that sent out 9911
If you dialed 8911 with no digits to follow you were sent to an "insert digit pattern" that sent out 9911
If you dialed 1911 with no digits to follow you were sent to an "insert digit pattern" that sent out 9911
We though of every possible way it would be dialed and built a pattern for it.
YES......my hotel product always used ARS......no exceptions unless a dealer foolishly changed it
In addition we had the front desk alerted when any of these patters were dialed. When emergency personnel arrived at the hotel, the front desk clerk was ready to direct them to the room which dialed 911.
Once again, we're making laws for people who do not think!
I did this over 30 years ago! I also asked for it to be hard coded into the software but it didn't happen.
I believe all systems still have ARS or LCR or what ever you want to call it. All they have to do is hard code the patterns in the software!