Just because someone could be identified doesn't necessarily mean that some lunatic (or group thereof) wouldn't attempt it.
I'm vaguely familiar with that station, from what I remember there's a very large mezzanine level that's below the street but still upstairs from the platforms, I imagine that's where it's going to be used.
Now that you've forced me to think about it, if it fell onto the tracks at the point where the train exits the tunnel then the train is still going at considerable speed. If at that point it broke rather than slid (caused, say, by a protruding part getting caught/jammed between a tie and the ground) then the scenario could end up being very nasty.