In the past I've always used: caller-id-override emergency-outbound 5555555555 to make sure that all 911 calls on our PRIs are sent with the correct registered E911 CID. This has worked fine until recently when one of our customers accidentally dialed "1911" by mistake. The call didn't match the caller id override rule and thus was sent out to the carrier with the wrong CID.
What would be the best way to prevent this in the future?
I'm surprised that this call even routed to the PSAP at all.