Making huge black and white prints was once routine in pro labs. Typically a Durst or DeVere horizontal enlarger on tracks, a big magnetic wall easel with a feed at
one end for the paper roll, Rodagon G or Apo Nikkor lenses. Machines were available which allowed roller transport from one trough to another for smaller operations.
The big outfits had more automated stuff. Large drums would be difficult to use with soggy fiber-based paper, but I've seen a couple models with some kind of internal retainer system or mesh support that would allow up to 40x60. They'd be quite rare now. Hasn't Butcher largely moved on to inkjet machines for his big
stuff?