I take it then that it didn't, and probably never would, occur to you that they might simply be conducting reconnaissance to see if an attack is feasible? You do know that Al Qaida agents have been caught more than once doing that?
I think everyone in this thread has gone out on a tangent from what this story was all about.
I don't know if these guys are potential terrorists on a recon mission, or if they're a bunch of guys who were hanging out one night and randomly decided they should check the facility out because of professional curiosity. I don't really care. They were trespassing, which is an already illegal activity, which gives the police all the authority they need to arrest them and question them on what they were doing there. Seems perfectly reasonable to me.
What this article is about is having people call the police's "tip" hotline when they decide they see others do "suspicious" things that are perfectly legal. I have a problem with that.