Just Browsing,
Yes and no,
1) Yes but only on request or special arrangement (the RAF Firefighters at Wittering for example will turn out to RTA's on the A1 in a reciprocal arrangement with Cambs F&R)
2) Didn't say that, some airfields Lucas, Lossie, Leeming have always been staffed by AFDFS (or civvies), other units Brize Norton, Kinloss, Honnington etc are staffed by RAF Firefighters. RAF Firefighters specialise in aircraft only because of their location on airfields (as do CAA firefighters and local authority bods at airports Heathrow, Gatwick, Manchester) but their training encompasses all fire fighting techniques. Some military airfields have a locally employed civillian element on crew working alongside the RAF Firefighters, Akrotiri, RAF G (thats about it nowadays) etc.
3) Yes
4) Yes (Cranwell for example)
The firefighters on board RN vessels are not full time trade firefighters, each ship has a fire party on watch commanded by the officer of the watch. Aircraft handlers on the other hand are fully trained firefighters whose sideline is aircraft turn around, RHAG maintenance, these guys provide fire cover at Naval Air Stations using RIV's and Major Foam Tenders. There has never been a Fire Fighter trade in the Army, the Army Fire Service always comprised of civilians employed locally by the Army, Catterick, Halton, Aldershot etc.
There are over 22,000 LA Fire Fighters in this country, the full time millitary fire fighters never had the strength to cover all these posts, the RAF have always provided specialist BA teams during FBU action, go back to the 1973 Glasgow strike and before.
The military fire fighter has always done well on these occasions, and will in the future, it's part of the job.