From Yobodashi.com (I've never heard of it either) and via Dragonautes2010, there's a link on clear "blind box chase figures" which, I think, may be partially speculation. The clear characters shown are NOT the figures from the assortment (which may or may not be blind boxed), but rather, are clear versions of the single ones being sold in Japan come September.
As a collector who is very interested in this line, I'll happily track down a convention exclusive or a store exclusive within reason. But rare insert chase figures which may be cherry-picked and/or sold on eBay? I'm gonna pass, thanks. Just give me the painted ones.