Much, much of the grade on both sides of Montgomery is very visible. I know people who report having hiked and mountain-biked the ROW.
At the summit of the pass, the only remnant is the deteriorating box car body that was once on the ground next to the train-order office and some of the grade that has not been wiped out by the present highway.
Elsewhere along the line water tank foundations, culverts, fills, retaining walls and the like still exist. If you use the search function of this site you will find a number of postings over the last year or two that show such.
Brian Norden