One of my first memories is riding behind one of those switchers at an Armed Forces day during the Reagen years. Back then Picatinny was so much different...different for the better I'd have to say.
The tracks still exist next to the ammunition bunkers and at least one switch is still operable, though the Provost Marshalls seemed confused as to why a former Marine would be so interested in abandoned railroad tracks.
The tracks lead from a gate near Route 15, through a wooded area of little note, over an old bridge traversing a creek. They then pass between a ballfield and some of the typically ratty housing designated for those who defend our nation (why we spend billions on bombers for a war we won two wars ago but find it hard to fix leaky base housing is beyond me). The tracks then split into a small, three track yard, which end prematurely where they were severed by shortsighted government policy.
Aboard the deeper innards of the base, there is a substantial yard by a power plant (since converted to gas, hence the end of railroading aboard base), crisscrossing abandoned ROWs, some narrow guage rail in place inside older buildings slated for demolition, and the old ROW leading to the north end of the base and, eventually, the junction with the NYS&W. Some of that ROW has been obliderated by housing, but most is walkable.
Rail on Picatinny, unless government policy swings wildly towards fuel conservation (highly unlikely), is dead.
As I stated a few posts above, the only hope is if the Base Closure people decide to do away with more vital defense infrastructure and turn the property over to wealthy commercial developers.
Be well. Do good work.