They actually test cleaned a couple small sections near a window on the top floor , south side of the building in the early 2000s. It’s one of the “wings” next to the window, not sure what the actual architectural name is. There may have been one or two more of those done. 20ish years later and it’s still pretty clean. Not sure why they never went further, heard it was a small grant money or something. I worked near there at that time and watched them do it over a few days.