Most likely it was done using some sort of tilt lens like a Lensbaby, made by LENSBABY, INC.
[url="http://lensbaby.com/index.php"]http://lensbaby.com/index.php[/url]
Vaseline is an old school trick.
Other films you could see something of the sort (not sure if they use a lensbaby) includes Deakin's [i]Assasination of Jesse James by the Coward Robert Ford[/i], and Kaminski's [i]The Diving Belle and the Butterfly[/i]
Of course, Deakin's could have used vaseline as well. However the effects look pretty heavily controlled. Yet, he is a god so not that he couldn't have done what he did with vaseline, I'm just assuming he used a special lens.
Anyone with anymore info?
-Mitch Monthie
Aspiring DP