All, Interesting enough, no photos on PATH is true. I rode PATH yesterday and the train I got on at Newport to Journal Square had nearly no one on it. I approached the conductor and asked about this policy. She confirmed there is a no photos policy on path. She told me that there are placks at each of the stations but the writing is very small and she didn't know where any of them were. She also told me it's in the online rules (as Bill confirmed). Of course I had to ask why and she indicated she really didn't know except that is probably had to do with security.
I've been riding PATH on and off for the past decade, never knew...
And Bill, I hope this doesn't seem like I didn't trust you. I honestly didn't see your final response until I went to post this. I asked the question so I figured I would post the conductor's response.
Tony