The rendering is a bit weird. It's disorienting to have the trains simultaneously underneath the map and occluding it. It also seems like the z-buffer is not being used correctly when rendering the train cars.
I wonder how much work it would be to actually handle them being underground/overground at appropriate places? e.g. the District Line and/or Picadilly near Hammersmith. Would be cool!
There's also something wrong with the map alignment. I think the tiles are being rendered with the wrong placement - the underlying map doesn't match reality.