I've never experienced it but I've been told that if an emergency responder needs to enter an area where classified information is stored you let them in, escort them, and security will debrief them and have them sign an NDA after the fact if they saw any classified information.
> you let them in, escort them
My understanding is that the fire department has pretty broad legal authority to tell you where to shove your policies your if your building is on fire. They can legally smash down your doors, haul you out kicking and screaming, and detain you outside of the building while they put the fire out.
This is largely correct. However, staff also need to be trained and drilled on security policies and procedures. That's often lacking, especially if security is outsourced to third party contractors.