Unfortunately the electric mouse traps need to be used in a dry environment. They work really well, no bait and take advantage that mice tend to travel near walls. They walk into them, get electrocuted and end of mouse.
While most if not all urban sites ban the discharge of firearms within their defined area, air guns are an entirely different matter.
Air and BB guns are not regulated by the Federal government and BATF. As such each municipality is free to regulate them in any manner they see fit. Some...
Yes, definitely do not "poison" if not on your own property. If they are within the railroad right of way, you will likely need to contact the railroad.