aeb - It's possible ( do a search on Soarin' - as I know i've typed this up several times now ).
They are doing limited sneak peeks for the ride, to give the CM's practice loading and unloading people, that way they're ready to go when the Cast & Passholder previews roll around, and so they're ready for the grand opening.
There really is no way to tell if they are going to do it that day, You just need to show up and see if there is a line that leads into "no-where."
update: There is no schedule for sneak peeks, past the cast preview or the annual pass preview, You just have to go see if it's running if your there before the grand opening.
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