Sanitation works

I was just walking on the street in Guber area of Shanghai at noon, when I saw a group of sanitation works is required by their manager who looks much younger (maybe graduate) gather in order to take pictures for them.I guess it's time for them to have rest.

As far as I know normal working time for these workers in Shanghai: 800 am - 1150am, 1400 - 1800pm; but according to public domain, some guy said they have saw the sanitation workers in appear on the street in their residence area at around 400 am and work til 900 pm. They are involved in the temporary contract with month salary of 1600 yuan...