I don't know. I was one of them, though, and it was packed. The line to buy tickets at the Vienna metro station at 9:30 was over a mile long. Eventually, they just let everyone ride for free because they couldn't keep up. The metro was over capacity for hours after that. I did the same routine at the 09/12 rally last year and as crowded as the metro was then, it was far worse today. FWIW.
Very cool.
A Freeper who was at Vienna (and left after two hours) is sending me pics. I will post them on the live thread.