[lightman]

There are tankers involved:

[T.B. Yoits]

Products that are not worth moving by truck due to restrictions, weight, or volume, usually go by tanker cars.

They're not just liquid; many are plastic pellets and serve small manufacturing plants with their own rail sidings.

[Spacetrucker]

I believe the other gentleman was correct, to a point. Intermodal trains generally do not have tanker cars in the line, but the story did say there were 3 different trains involved, so it sounds more like a switching station malfunction.