Though Al and Rooftree and your hints make it easy, " I think" it is here
https://maps.njpinebarrens.com/#lat=39.81507035004341&lng=-74.2418037260238&z=20&type=nj2015&gpx=
It's been a really long time I've on the RR grade but that area S branch has always had a nice sand bottom and clear water. Didn't the PPA do some tree plantings there not long ago? The RR grade is blocked off to the North now or it was, how do you access, from the South?
The N branch, Al's pick is a bridge that was blown up then rebuilt. I remember Tom Brown had a teepee on a "hidden" trail deep in the cedars. The Factory branch is or was elevated and looks nothing like the surrounding woods of the S branch. I never gave any thought to the powerlines but I remember that being filled with jagged large concrete chunks ready to slice a tire or get hung up on the undercarriage if you picked the wrong line
RATS, beat by Joe by 7 minutes as I was typing!!