Comment by ghaff

Financially impractical as all this already is, as the article points out, dealing with private railroad cars is such a tiny blip that it's hard to imagine anyone responsible for the logistics of a large-scale rail operation wanting to deal with it. It's pretty much only (sort-of) supported by Amtrak for legacy reasons.

As you say, there may be short sections where this sort of thing could work but that's probably not what people looking to do long cross-country trips are looking for.