What do you think they are doing?
They ain't do'in nutthin, they just sittin around!
The scraper box behind the horses tells me that they are excavating the hill side (roadbed) and dumping the dirt into a transport box to fill in somewhere else.
The handles of the scraper box can be seen below the man holding the reins of the horses.
I agree with Jack, but the transport box seems to be sort strange looking. That might be excavating ballast for the RR tracks.
Optical contusion? Looks like a building on the left behind the trees.