For now, train stations maintain a good balance of spacing that allows for trains to all have a decent amount of space to themselves. One day though, spacing will be a more pressing issue in the world and this design company is trying to take trains out of the equation.
Seeing a train hanging vertically from a building is probably something you don't see every day -- or ever, given the fact that trains never hang from anywhere. This concept believes that with the growing competition for land and the ever shrinking amount of free space there is, it would be a good idea to have vertical hubs to 'park' trains.
The concept is a bit outlandish, but it stands on a firm concept that would definitely decrease the amount of space taken up.