Pretty easily really. Bad grass fire or brush fire. You can get a grass fire from the train itself if it's dry like it is and you get a spark from the rails. Those old bridges are creocote soaked timbers, burn like crazy.
Walleyes, I am surprised that no one has flashed up the "Big Bay" trestle yet!!!! Maybe it is too short to make a fire similar to the Mayerthorpe trestle.