So...after an "Aicraft Accident" the said a/c is on fire. IF you know the total POBs and they are all accounted for.
So how are you going to quickly account for all the souls/persons wandering around in all directions on your nice big open airfield following a crash / fire / emergency evacuation? (Think Air France A340 in Canada for example)
Pob / SoB is largely irrelevant to Airport Fire and Rescue, because unless the number is very low, you aint gonna find, and then count, everybody before a decision is made to enter the burning fuselage. Remember you've only got some 180 seconds or so before the cabin becomes non survivable.
AFFRS will attempt to get in there ASAP to check noone has been left behind.
BEX