It doesn't seem "planned" at all, despite its mastery. Her story is going out as tweets, to be serialized in 10 segments, and to run in the magazine in two installments, stored at The New Yorker's new location, Page-Turner:
http://www.newyorker.com/online/blogs/books/2012/05/jennifer-egan-black-box.html
The new editor of Page Turner, whose name I do not know, and her husband bought my very good friends' former Brooklyn coop in Park Slope. (So I have sat, lightly, against the editor's new sink, pasta and wine, pasta and wine, adjusting my stirrups, and I have watched out her new, my friends' old, windows.)
Good stuff! Thanks for sharing!
Joe Winkler reviews "Black Box" writing in tweet-sized units at HTML Giant: