On Letters from Iwo Jima’s Screenplay Oscar Nod

I suppose I can understand the Academy Award nomination for the very deserving Borat in the Best Adapted Screenplay category, on the grounds that the character originated on Da Ali G Show. But can someone explain how/why Letters from Iwo Jima is nominated, alongside Babel, Little Miss SunshinePan’s Labyrinth and The Queen, in the Best Original Screenplay category, even though its credits clearly list the movie as being based upon Picture Letters from Commander in Chief? Is there some deckchair shuffling going on? Or did someone owe Paul Haggis (who receives story credit on the film, and thus would be eligible for an Oscar) a favor?