That's what I'm thinking, that they have preheaters.
But, thinking about it even more, railroad locomotives started to be equipped with dynamos (and later generators) in the late 1800s/early 1900s as they started moving to electric lighting.
Some of the first electric locomotive lights were carbon arc lamps, and you need a lot of juice to get those things cooked. Later incandescent lights became the standard, probably around WW I.
So, I'm thinking that the preheaters weren't steam, they were electric.