Appreciate the comment Wee Brian
however what you have to take into account is that no matter if it is one person on a track inspection or the more normal gangs of 20 + that work a night shift in enginnering hours the problem remains the same.
Due to the layout of the track and the fact the trains are still running a trackside fire would seriously place a person at risk as the M.O.E is comprised if for example and this is the norm escape is single direction to a place of safety(why? Due to limited clearence, train running, third rail, tunnels etc). Smoke as you know travles a fair distance especially in deep cuttings and long straights and would quite easily impede any escape.
As I am beginning to look into the problem it would appear that it is much more of a risk than first thought. Network rail employ a registration scheme and to date approx 170,000 people have track safety cards and given the amount of fires on the rail infra structure it is safe to assume that this a high risk.
In addition the staff recieve intensive training before going onto the rail infra structure and therefore you can deem these competent people and yet approx 10 people a year die through non fire incidents. This points to a high risk industry in which am convinced that a fairly large trackside fire whould have fatal consequences.