It seems like the sort of naive gimmick one might expect from a MAD Magazine cartoonist, or Elon Musk on a ketamine binge. It would work to an extent for a while, though whether the amount of electricity generated would justify the maintenance costs to keep it going is another matter.

The arguments against it are the power yield of a panel pointing upwards, and presumably covered with dirt shed by passing trains. That said, it would suffer less impact damage than photovoltaic roads/bike paths floated elsewhere (the occasional rock impact, as opposed to constant traffic). Also, there is a lot of track, so even if a segment generates little power, it adds up. Not enough to power electric trains, though possibly enough to offset the power bill after operating costs are taken into account.

I’m guessing this installation is an experiment to quantify these figures rather than a commitment to roll this out more broadly.