Matt,
PBX vendors aren't Inter-connected VoIP Providers, who are required to
serve E-911 wherever they deliver service.
You point out the disadvantage of Hosted PBX, but on the other side,
when the internet is down, voicemail will still work and failover to
alternate numbers should also work
A company called Teltronics (ww.teltronics.com) sells hardware for MDU
911 detection.
Hotels, office buildings, apartment buildings, and campus have issues
with final destination for EMS personnel on a 911 call.
I would like to suggest that if you offer VoIP, especially to the AZ and
FL crowd
The 911 call is going to use SS7 information like caller ID and address
from the LIDB database to send help.
Your script can't really do that.
If it could, you would need to test hck out of it and find a way to get
insurance to cover when it didn't work and you were sued for criminal
negligienc