Having been involved with a couple of large collaboration physics experiments (but not this one) I can relate my experience that everything is planned in advance in frustratingly great detail. I'd assume that someone promised to be able to transport it via the short route, and was simply unable to deliver, or that the design specs had to be changed after the contracts had been let or something to that effect.

edit: Note here that they started planning at or before 2001 http://www.katrin.kit.edu/130.php#Anker10