I can understand the fire services' frustrations with these sorts of incidents on the SVR, there's quite a few sections of the route that aren't easily accessible, or accessible at all, by road, by the very nature of the lines' rural location.
I was on an SVR train heading towards Bridgnorth one day earlier this year when a preceding service had set fire to a fair stretch of hillside forest about halfway between Bewdley and Arley. The fire engine passed through Bewdley at the same time as our train was departing from there, but because of the exceptionally narrow lanes that the fire engine had to traverse to get anywhere near the location of the fire, it soon fell behind compared to the progress of the train despite the trains' average speed of only about 15mph.
On the NYMR I've seen the crew of a steam loco use a small hose pipe routed from the cab to deal with small grass/bush fires by the lineside caused by a preceding train.