I have cleaned the inside of a few smaller tunnels. I 2 step walls and ceiling. A 50 ft tunnel that had all equipment removed last week took 3 hours. Usually more like 4-5 hours if glass doors are bad. Obviously these can be done much faster on some kind of maintenance schedule.
I have priced some using the strong hf acid aluminum brighteners as it takes a lot to get that stuff off the brick or walls and to clean up the aluminum.
I priced a tunnel at $400, guessing it will take about 3 or 4 hours with those chemicals, might 2 step them if needed.