Presumably, they have to figure out something if an inbound international flight is evacuated with some passengers taking evacuation paths away from the airport (e.g. the AF 358 crash in YYZ where some of the evacuating passengers ended up on a local highway hitchhiking to local hospitals or back to the airport) and/or may not have passports on their persons (i.e. passports lost in the crashed aircraft).
The recent Asiana crash in SFO would be another example of this.
Also, this week's fire in NBO, though I haven't seen anything to indicate there were inbound passengers being processed when the evacuation occurred.