No "question" here, and I don't know if the twins who created it use Arduinos, but if you visit...https://www.youtube.com/embed/ACkmg3Y64_s?rel=0
(or, if YouTube isn't your thing...)http://en.wikipedia.org/wiki/Miniatur_Wunderland
... you'll see an amazing model train setup. Actually, I should say "trains"… there are 890 of them (over 11,000 carriages) in this amazing layout in Hamburg Germany.
Trains and cars and boats and airplanes!
The YouTube clip is pretty amazing in itself. Sadly only a glimpse of the electronic control systems... maybe an Arudino person could undertake a "tour for techies"!