Just found this via the girl.

First it looks like a great guerrilla idea. And I think, this has been done before, but not with a projector attached to the train, but with screens within the tunnel. The screens were placed in certain distances and each one displayed one image subsequent to the image of the previous screen. This way the people on the subway saw the film on many different screens, each one of them just showing one step of the animation. Like a thumbnail cartoon (or whatever they’re called)

I just wonder, if this kind of marketing tactic is feasible these days? (See the comments to the blog post linked to above).
If you tried this in any big city today, poeple would panik. They would expect an act of terrorism instead of an act of advertisement.
So, summing up: Don’t try this in your city. (In fact, don’t try this at all.)