I am used to seeing these guys from the inside of my office. I used to work in the BHP building in Perth which is the tallest. The window cleaning team made up of about 6 people all taking 2 widths or glass each. they used to abseil over from the top which was 45 storeys up and sit on a plank of wood to clean the windows.
I am surprised they could get close enough to the windows with the size of the balls they must have had to do the job!!