Hummmmm! Interesting. Am I correct in presuming it is some sort of sealant sprayed on the surface of the load to keep the dust down? Seems to be a two part process, as each arch sprayed all the loads. Seems they don’t want to overspray much, very accurate.
Wouldn’t think it would be too hard to model, even from what you see there. A couple of arches made from girder material and some round stock for piping. Would seem there would be a servicing house close by and a tank to hold the solution. Up the hill maybe?
Never have seen one or a kit for one. Maybe someone has. Give one a scratch building try and let us know what you came up with.
Have fun,
Richard