There's no hope of moving the shale with just a couple of rakers on each bend and an ancient tractor with a simple grading contraption on the back. That hasn't changed in years, so doesn't reflect the change in the track or the machines.
Surely someone could put some thought into a grader fitted to a tractor that actually shift the shale back towards the centre/inside of the track - it needs some sort of blade at an angle, at a fixed height. Get a decent tractor (or two), with a good width of grader attached, and it/they could get around the track fairly promptly.