I was once in a tunnel with a group of people when one member of our group fell and broke his leg. In that case, we happened to have a paramedic in the group, and we all teamed up and got him splinted and carried him out of the location, then called rescue, so we didn't have to deal with the trespassing issue. In our situation, we were in an extremely remote location and we knew it would take many hours for rescue crews to even get to us. We were able to get him out of there in probably less than an hour.
That being said, had we not happened to have a paramedic in the group, or had the injured person requested it, I would have called rescue crews in a heartbeat. It's better to take care of safety first, and deal with the legal ramifications later.
Here's another interesting, relevant thread:
http://www.uer.ca/...=104264&currpage=1 The news article in the OP on that thread has moved, so here's that link:
http://hennepin.ks...der-pillsbury-mill You'll have to sift through some drama to find the actual story in that thread...but if you ask me, that guy did
exactly the right thing, and did NOT deserve the criticism he got.