FYI for anyone else who may be interested in knowing the answer to this.
Got an email back from Bonnaroo. Basically they do not even give you the tickets until you board the shuttle. I like the concept of what they're doing here since it seems to be intended for locals but they should probably shuttle from some of the other locations. Honestly the optimal solution would be to have shuttles from the Boro at the same location as the hotel package folks but without the hotel package.