Of course it stops when they respond to a crash- and that's not often. In the USA the Unicom is not prescriptively regulated. Just a fantastic zero cost improvement to safety.
In the USA like all other modern aviation countries the RFFS is run by the local airport and the Firies are multi skilled . They do lots of other jobs when aircraft are not landing or taking off. Just commonsense. The coalition decided to bring in this system under Mark Vaile but it never happened .
Under Mr Truss and his advisors nothing will change. Our current RFFS costs per tonne landed are about twice that of NZ where it is competitively provided.