I remember being stuck in that subway tunnel while we were making MacArthur (movie) - it subbed for Malinta Tunnel in the Phillipines - spent several days there, rigging electric cables into the tunnel and then lighting it - fun even though that heavy copper got heavy and old fast. You could still see the remains of the old PE station and yard at the entrance. - Hiked in but it was blocked a couple of hundred yards in. No exploration for me that day. Got a chance later, but the "Bunker Hill Project" closed it off forever, but pieces still exist even now. The Apartment complex that replaced the old station has covered the old tunnel entrance with concrete, but there is a nice mural of the PE cars and tunnel in its place.