I was thinking of saying a "subway car" but this is the San Francisco Bay Area Transit District (BART) and not sure how familiar some would be with the name. I've seen oddball items being repurposed. Like retired shipping containers for a beer garden or an old plane being turned into a restaurant.
https://www.sfchronicle.com/bayarea/article/BART-is-adopting-out-old-cars-Here-s-what-16994973.php
https://www.sfchronicle.com/bayarea/article/BART-is-adopting-out-old-cars-Here-s-what-16994973.php