Back to School?
http://www.appleinsider.com/articles/08/05/29/sources_apple_planning_biggest_back_to_school_promo_yet.html
I think maybe they're shooting a commercial for their back to school promotion. That would seem about right, because apparently this is going to be the biggest year ever for their back to school discount program according to the article.
Unfortunately, I think this might be the most likely reason for the filming. I'd love to be wrong though.
jW