Many years ago, I was told that H&M planned a second set of tunnels running south from the junction near the Hoboken station to the junction of the lines to WTC and Journal Square/Newark. The tower which controls the junction at Hoboken supposedly was placed in the entrance to the second set of tunnels, and there were staircases constructed from the Pavonia/Newport platform now in use to the platforms of the lower set of tunnels. Is there any truth to this? When I last rode PATH, which is quite a few years ago, I thought that one could observe additional tunnel entrances at these junctions, but they did not have any track in them.
I've never observed anything like that myself. I will say it isn't too far fetched, i mean the astor place stub was built, and that isn't some little tunnel start pocket it's a good 35 feet back from the elbow there.
The only questions i've ever had based on stuff i saw were about exp and pavonia/newport stations.
They may be construction remnants where they staged excavated material for removal above ground etc, but not actual planned tubes.