Here is what I would like to accomplish.
Have an outgoing route for 911 calls. Depending on the trunk the call goes out on, the caller ID should be different.
If the call goes out on trunk that is 1st preference of trunk sequence, then use emergency callerID of extension. If user doesn’t have emergency CID set, use our general company CID. If call goes out on trunk that is 2nd on trunk sequence, only use general company CID.
FreePBX has a built in emergency route, please RTFM and ensure your VSP is compliant.Generally you have to pay for that by DID with the provider of that DID, and non compliance could be VERY expensive liability wise. . .
Generally it’s called E911 compliance and if you can’t fullfill you will need to place a big sticker on every phone, stating explicitly that calling 911 is NOT an option,.
The thing is I have E911 address set for a few DIDs with my provider.
Our LAN extends over different street addresses and I have a DIDs for a few selected users there, mostly for E911 purposes.
Now when they call 911 and the trunk with the provider I have the DIDs+E911 with is up, it’s all good.
Now what do I do when that trunk fails and I am rolling over to a trunk with another provider where I don’t have E911 address set for that other providers DIDs?
I would then rather send a different CID.
E911 requires an absolute location that the big red trucks will roll to when you call that number, if you go out of a non E911 complant trunk, well . . . .
That would be when you are liable, someone is dying and you sent the 911 call to a center that has no knowledge of WFT you are, think about it . . .
You have a remote extension currently in Cuba, HTF will that work, again, Think about it. . . .
( you are just not allowed to have trunks fail that are calling 911, 
or you might end up giving your company to the lawyers.)