"Berlin police told the SID news agency that a technical failure sparked the fire as the train was pulling out of the station..."
That looks like some significant "technical failure" !
A difficult spot to access for rescue, too.
The fire department can't spray water on it, because it's an electrified line (you can see the towers and wires) -- not unless they want 12,000-25,000 volts coming back down the hose at them. So they would have to contact the railroad dispatcher and get the power turned off. That takes time.
Looks like it may have been confined to only one car. Wonder if food preparation was involved?
Article says it's a privately-owned train. Probably one of those deluxe tour trains.
Definitely "a trip to remember" !