I don't think it will affect the RFF category for many airfields if any. The big difference is when a full emergency is declared, or an accident is imminent i.e gear stuck and will not come down, the local brigade are usually at RVP points at the airfield in anticipation of the forthcoming incident/accident.
That is where I suspect we will see the difference. On strike days there will have to be a smoking hole before the local brigade will turn out.