Your post got me to wondering if I could trace any of this grade on the aerial photos. I have absolutely no reference material on this line so I am relying on what I can see and any topo data. I was able to find the southern portion of the line on a topo map so I had a starting point. The modern topo only provides about half the length of the line stopping around the ponds in the middle of my map. I forged further assuming that the road was the old grade due to the curvature. I wasn't able to make it all the way to the mine though. It gets a little tricky up there. Here is the start of my map none the less. From what I have read there was a double loop up near the Iron Mountain mine which is marked with a yellow square.
Iron Mountain
Dave