I don't know about California, but in some states there are special sections of the criminal code relating to railroad trespass. I am aware of the fact that penalties for railroad trespass were recently been increased in a couple of eastern states, and California may have also strengthened its code. The issue is twofold. First, the demands that railroads act to keep hazmat traffic secure - especially TIH. Equally (or more) important is are tort liability actions carriers face after a trespasser is injured on railroad property. People who have no right to be on the railroad often sue (and collect). A defense against in those cases is that the carrier took reasonable steps to prevent the trespass - including policing its property, posting warning signs and participating in community awareness activities like "Operation Lifesaver".

One example of how stupid these liability actions can be is the West Virginia case where a woman was hit by a train while walking down the middle of an active railroad line listening to an I-pod. She sued the railroad - contending it had failed to warn her it would be operating on that day. Fortunately, she lost - but that idiot still cost the railroad money to defend itself.

I have little sympathy for the woman who was cited by the UP officer. Stay off railroad property.