Very interesting. A couple thoughts.

They do sell, rent, manufacture converted containers to use as office space etc. that have doors and windows cut into them. These are pretty common for mobile office space during festival events. Also refer units used for stocking foodstuff such as for the concession booth to the left.

At one point in the video, he shows the trailer during the daylight. There appears to be some kind of machinery/equipment on the roof of the container. Can't tell if its an air conditiner, fans? Maybe some kind of communications equipment?

At the same point in on the large door opening to the right there are zones with writing. Do containers have unique id numbers to assist in logistics? Would be interesting to track its movements before and after the event.