Probably one step back. Without knowing precisely how the bidding system goes for Polish subway cars, I'm going to guess that there were multiple competing bids for building new subway cars. They were all about the same, except one of them said "Lookee, our cars will be recyclable!"

The critical reader might, at this point, say "Hey wait a minute, subway cars are made almost entirely of metal and metal is always recyclable, so you're really not saying much of importance there". However, it suits everyone just fine to pretend it's a significantly greener option, from the company to the politicians to the media outlets who publish their press releases, so here we are.