Seems to be a Hydrolic Pumping Machine....after the BOBYRN's will unload the stone chips, I have seen this to set up the tracks & make same level with the stones....same as you see in BMRCL construction sites,some Hydrolic pumps will move upwards & go down & the process continues to dig the soil....Here it'll not dig anything but just put some pressure on the tracks.Works on the basic principle of Pascal's Law.Normally accompanied with PWD trolleys.