The idea is that, initially, all cars had toilets (see the invisible emphasis of "only" in "if only fifty percent of the cars would be equipped with a toilet").

The idea is that, initially, all cars had toilets (see the invisible emphasis of "only" in "if only fifty percent of the cars would be equipped with a toilet"). Of course, there must have been plenty of cost associated with handling toilet complaints and training (and re-training) at the shunting yard, but we can guess that the long term savings made up for that.