Those ponies with masks were up for preorder on Toywiz with a listed release date of March 23, though some people are getting them today, despite Hasbro saying they’re to hit shelves in fall 2013.
Above is the backcard for Sunset Shimmer. The blurbs read “Sunset Shimmer knows a magical path to faraway adventures! Years ago, she was also a student of Princess Celestia!” The second reads “The ponies wear beautiful masks to dress up for a special celebration!”
So it seems that these brushables are in stock over at Toywiz, though they’re not listed for sale anywhere else. Keep an eye out on your local stores to see if they make their way over.