I _think_, although I'm definitely not an expert on that stuff, that you rely on a keyless-entry type of actuator that pulls the inside door release for you. For power failures there'* probably some sort of hidden emergency cable-pull opener like for locking gas-cap doors.

I guess it'* just like patching any other big hole: Slap a piece of metal over the hole where the outside handle used to be, and Bondo it up.