I just have to ask the OP...since one of the inspirations for this interactive's elegant design is Edward Tufte, did you take inspiration from his version of Harper's annotated hospital bill? Because that was the first thing I thought of when seeing the beautifully-done annotations alongside the dense subway arrival time data.
There are lots of influences from Tufte, the image you link was one of them for sure. We tried to incorporate other ideas like fully integrated text, numbers, and graphics and showing comparisons and causality. Bret Victor's work was also a big influence. If you are interested in what the design and implementation looks like and are in the Boston area there's a meet up this Thursday where we talk about building this:
http://www.meetup.com/Data-Visualization-in-MetroWest-Boston...
The chart I'm talking about is in Tufte's Envisioning Information, and is one of my favorite examples in all of his books: https://pbs.twimg.com/media/BpxpK-1CIAAl2yH.png:large