There is a media event scheduled for April 30-May 2 which includes a "preview" of the ride.
http://www.**************.net/headl...fs-mine-train-mymagic-and-more-new-offerings/
Might be in soft opening before then, but the fact that they are characterizing it as a "preview" suggests that it won't be fully open at that time.
That's just conjecture on my part, though -- perhaps someone more in the know can chime in.