Do airport fire departments have to have airstairs? On the video of the JetBlue 292 landing (at 4:27), one of the first emergency vehicles to approach the Airbus is a fire department airstair. I've never seen a fire department with its own airstair. I found a standalone picture of LAX's Stair 80. I don't see a stair among ORD's fire apparatus but DFW and DEN have them. Why do some airports apparently have airstairs but others don't?

The only reference I found from the FAA is a 2012 article about New Large Aircraft (e.g. A380). Relevant passage:


  Several airports are now acquiring mobile air stairs and modifying
  them for ARFF use with hand lines, ventilation equipment and fire
  fighting tools. Some European airports have even acquired customized
  platform vehicles for rapid firefighter access into aircraft. Ideas
  being discussed are various air stair designs, scissor lift catering
  style trucks and modified ARFF vehicles with stairs or ladder that
  will accommodate all sizes of aircraft, including double deck designs.


I found this manufacturer page touting the importance of fire department airstairs. So obviously they exist. Here are my questions:


Does the FAA require fire department airstairs?
What are the primary uses? Getting passengers out or getting firefighters in?
Sorry unfamiliar with FAA regs, but since Canada's regs are often just rewrites of US or ICAO rules:

In Canada, I cannot find any direct reference to airstairs as required minimum firefighting equipment : Canadian Aviation Regulations (SOR/96-433) section 303.09
there is however a requirement for holding an airport certificate in Canada requiring a safety management system be in place, this involves doing a detailed risk assessment. 

logically having the ability to deplane any aircraft expected to land might be seen as a necessary risk management solution to a number of potential possible issues. There are similar requirements for "air operator certificates", meaning some of the accountability may be place on the airline. Like so much of Canadian law, we will probably not get a definite answer until a large number of people die and the courts get involved.