facepalm... looks like 3cx missed the boat in new beta release.
https://www.3cx.com/blog/releases/update-5-pbx-crm-integration/
Emergency dialing (911)
Although 15.5 already supported emergency dialing, we have made two notable improvements:
You can now configure per group – or range of extensions – which emergency number they should use in the outbound rule. This greatly simplifies configuration.
Emergency calls no longer go against the license limit – they can always be made (providing your SIP trunk has the capacity).
this sounds like what we are asking of the per group or range of extensions, however when you watch the video it is just selecting which trunk those extension (groups) go out when calling 911 and not changing outbound Caller ID...
FYI, we could already do this all you did is move where we do it for emergency calls this simplifies nothing!!!
Also, how does this help for PRI deployments?
Let me help with the statement of "shouldn't be using old PRI for new VoIP PBX deployment".
its called being in a contract.
The ability to set outbound Caller ID should be a basic feature that any phone system should have.
Good to know that emergency calls aren't counted towards license
again, anymore?