They were most likely water jetting, where they have extra person from the supplying company normally to turn the water generator on/off, changing pressures, maintaining the system while running and also deploying and recovering the hose.
Hot and cold is just on and off pressure when cleaning.
Not sure where you would gain employment in this other than the supplying company.
Good luck , on the job front Ullevi,
oh! i for one thought it was a fair question.
