Well, one way of doing this is to have incoming calls go to an OGM where it executes a small program that adds several numbers to dial to the outbound list. The outbound list can be configured to play an Emergency message. And the result is an incoming call that triggers a program to fill IVM's outbound list with numbers to call and play an emergency message to.
It is also possible to configure in the outbound list settings what happens when a call is not answered or sent to a voicemail and then execute the appropriate OGM to handle the situation.