I was more than a little skeptical about the "hooking up" story and said so when I posted it. There's about a hundred other variables, too. Quality and lump size of coal, firing patterns, how hard an engine might be working, etc., etc.
My own opinion is that vegetation growth patterns, a possible long-term drought, and the lack of trackside defoliation--either by removal, poisoning, or fire--has made it easier for locomotives to start fires and for those fires to grow rapidly once ignited.
There is plenty of blame to go around for this: almost a century of fire suppression by the Forest Service, lack of logging to remove unhealty trees and to thin overgrown stands of trees, unreasonable attitudes preventing sensible removal of trackside brush. Ironically, if a locomotive starts a fire, you can bet that everybody will blame the railroad for it, but--in fact--forest management policy is probably much more responsible. That cinder was just a convenient ignition source.
One final brash statement: I've lived in Colorado for all my nearly half-century life and have taken an active interest in forest management issues for much of it. I've never seen our forests in a more unhealthy, fire-prone, diseased condition than they are right now. Fire suppression AND logging suppression conducted TOGETHER are fundamentally imcompatible and will create the kind of tinder-box forests that go up in ecologically and economically disastrous conflagrations like we've seen in the last few years. You can't have it both ways.
Now let the other kinds of flames start!