Unfortunately the pic is not of too great quality. But.... the foreground vehicle is a BZ-35 refueling truck on the ZiS-6 chassis. The one on front of the BZ-35 is a BZ-38 on the GAZ-AAA chassis. The two next vehicles in front of the BZ-38 don't seem to be the refueling vehicles but the fire trucks PMZ-40 on the ZiS-5 chassis. The two last ones in the background , still going clockwise, seem to be the BZ-39 or 40 refueling truck on the ZiS-5 chassis IMHO.
Do you have a link to information on the PMZ-40? I can't find any information about it. The rear of the two trucks seem to be different--one has a box mounted low. I thought that they might be VMZ-40 and VMZ-43 oil-water filler trucks.
I think I was confused by the caption of a drawing sheet that stated that it is the PZM-40 and PZM-43 fire truck. The profile there looks exactly the same like for the VMZ-40 and 43. The two vehicles in the pic can be the VMZ trucks but the VMZ-40 is more likely than the VMZ-43. The VMZ-43 had a big tube on the roof that was a folding chimney. Also there were two quite large hatches and big boxes on sides of the truck. Contrary to that the VMZ-40 had two small hatches and a small folding chimney and no side boxes. The box ( it was a cover/container rather ) at the low back of the second vehicle could be dismounted or just lost for some reason. So taking all that into consideration I would say that the VMZ-40 oil-water filler truck fits better to both of the vehicles there.
Here the missleading drawing..
and here the VMZ-40 without the box at the back ...
You're clearly correct that it's not a VMZ-43. However, the box on the back of the VMZ-40 doesn't seem to have been particularly detachable. It was storage for the nozzles, so I'd think it was pretty important. Of course, if the box is crushed in a low-speed crash, you just figure out some place to put the nozzles.
I see. But the box was a piece of a steel plate and it was just a cover for valves you could connect the refilling hoses to.. What is more the cover could be or not. Believe me it wasn't important for Russians at all. As a former military who worked with the VVS regiments I saw enough to be sure of that.
Here is an example... damaged VMZ-34 with the cover and without ...