It's a nifty idea, but sadly there's some problems either with the data, or how the data is being handled - it's currently showing trains running on parts of a line which are shut down for engineering work this weekend. (Northern Line, Camden to Charing Cross). There's also a train running under Bloomsbury without a line to run on...
It's more a work of art ;-) I basically show the data I get, but I don't fully understand it all - those Northern line trains all have a 477 id, which I think may be ghosts or tests or something else. Trains can jump lines if they're, for some reason or misparse, going straight from one station to another much further down the line.
So cool but not quite trustworthy!