Actually, the T is a mix of catenary and 3rd rail systems. The Green Line (the light rail pictured in Joe's initial post) is cat-powered throughout. The Red and Orange lines are 3rd-rail everywhere; above ground they run on a fenced-off right-of-way. The blue line (at least the last time I rode it) ran 3rd rail underground and catenary outside. I am always amazed at how cavalier T workers seem around the 3rd rail, stepping over it to cross from Wellington station to the car barn. I can only guess what the OCP is on that circuit :-)
/mike
