Probably inevitable - BUT - It sure seems like the big ones I remember in the Southwest USA area the past few decades have mostly been human caused. Campfires left unattended. Fireworks. Intentionally set by miscreants. The lightning-caused fires seem to be smaller and less severe. Perhaps my memories are jaded by the extended media coverage for the human caused ones - the fire, then the cause, then the finger pointing, the trial, the jail time/fine, etc...
I certainly hope the train is not found to be at fault here, but either way I think it is in the D&S's best interests to take even more steps to protect their interests here. I do remember attending some kind of ranger-led discussion about how they determine the causes of wildfires and it was pointed out that in most cases it's not too hard. Once you figure out where the fire started, there aren't too many options left as to how.