I've seen that elsewhere, with various types of cars. The ones I've seen were usually riveted tanks, probably retired because they exceeded the years-of-service rules. This one looks like a newer tank.
Another example of recycling, to go with the flatcar-bridges. Maybe a way to use the cars one has replaced with newer, better models. Add some boxcar-sheds and the stockcar-feed storage buildings common around Billings, MT, and one could use a lot of junkers.
