1. You define network region and ELE in the network-map.
2. If ELE is configured on the station form (at a more granular level), it overrides the ELE in the network map (at a more global level)
3. Network regions can have locations too.
4. If your stations have the 'location' statically assigned AND the network-region match in the ip-network-map end up being different locations, I don't believe CM will send the ELE for a phone in the subnet in question. It will see inconsistent data for the static assignment of a location on the station form which is different than the location assignment based on that phone's network region and CM won't, for example, send a ELE of NYC# like the network map says for a station with a hard-coded location in SF.
5. ELE from the network map only applies to ARS calls of type ALRT. If you have 311,411,511,etc as type svcl for 'service call' - that's fine. But your 911 calls as svcl will always work despite not triggering emergency treatments like ELE or crisis alert.
6. Your carrier has some configurations in play here. You might be able to send out any # you want, or just DIDs on your service for normal calls, but when it's 911 and they're handing off to the PSAP, their default, in my experience is that it's always the billing number or main number of the service that is passed along to 911 unless you have some paperwork signed taking responsibility for being able to send different numbers (like 1st flr, 2nd flr, etc)
I've seen the odd bug in CM 6.3 where the ELE had to exist as a station, and there's some good reasoning to that. There's an emergency callback feature no by default. If that number in ARS that's alrt (911) calls back the DID in ELE to CM in <10 mins, CM will route the call to the station that placed the 911 call - that person doesn't need a DID, and your ELEs might be set per location in the building, whatever it is, that feature makes it so that when someone dials an alrt call like 911 that CM basically assigns that ELE almost like a temporary DID to the person who called. That being said, if 911 happened to say something like "we'll send someone for that less critical emergency in 15 minutes" and called back, the feature would no longer route to the caller. Now, if there were no other treatment in CM to route a call to the ELE number in the network map, the 911 operator calling back to check in on you might get a telco intercept that the number they're calling is not in service - not nice!
I'm not entirely sure CM requires that ELE in the network map be an actual dialable number, but it'd be crazy for it not to be!
If you want to get into things at an SM level, it's entirely different in terms of the components involved, but it's very similar. SM can have an ELIN SIP entity - it stands for emergency location identification number. That ELIN server can probe your network and phone registrations and data switches and come up with it's best guess for a physical location. If you're on a phone with a certain MAC address and they know it's plugged into data switch 3, port 12, and that the cabling leads to cubicle 17, the ELIN server can update SM with a SIP message to say that you're at cubicle 17, or to send out whatever number to the PSAP is most appropriate for cubicle 17 when you dial a a SIP URI that SM has defined for 'emergency'. It can do a lot more, but also requires a lot more in terms of planning.
