Just got off a Pacific Surliner train. Took a good luck at the bike racks. Three per car, hooks for both wheels with bikes vertical. There are cables about five feet long attached to the top hook. An eye of about 2 inches at the end. To lock your bike you'd only need to bring a padlock. You could probably snake the cable thru the frame and both wheels and use the eye and padlock to get back to the cable.
I took a pic but can't post a pic from my crackberry - maybe manana.