susie:

http://metrarail.com/metra/en/home/utility_landing/riding_metra/rail_safety_security/emergency_preparedness_public_awareness.html

Photography & Videography: For safety and security reasons, photography or videography on Metra property is only permitted in areas that are clearly open to public use. Areas that are accessible only to Metra employees, including but not limited to, the right-of way and rail yards, are highly restricted areas and are not able to be accessed for photography or videography by the general public. Metra will prosecute trespassers to the fullest extent of the law.

Essentially, according to their policy, as long as you don’t break into restricted areas to take pictures, you’re good.