Not exactly "current railroads", but... The Hudson Bay Railway, in 1990s CN days, was rather famous as an anachronism. Grain moved exclusively in 40' boxcars, mixed trains with F-units and steam-heated cars... But I clearly recall something more, which I can't relocate evidence of. In some book on Canadian railways, I saw a photo of a heavyweight car on this line. http://www.trainweb.org/oldtimetrains/Hudson_Bay/winter.htm This page shows one in 1976, already very unusual. But I remember seeing a heavyweight in VIA colors, and almost surely dated in the 1990s. Did this actually happen?
I remember seeing a passenger train video on this line. (A documentary?) It was all later era cars. A heavyweight in VIA colors sounds interesting.