I have installed several emergency sets and I have not seen a spec for fire protection.
It has been a few years since I spec'ed a set. Things may have changed.
-------------------- Ohm's law
Not just a good idea; It's the LAW!
Your local authority or insurance company may have a view on this.
In UK there is a standard BS 8519 which gives the design responsibility essentially to the building designer.
Essentially it implies that gensets will be located in a fire resistant room, thus any genset enclosures are for acoustics. it does not seem to cover outside located generating sets.
Assuming the concern is directed to fires inside the enclosure, then fire detectors and fuel shut off valves are often specified.