the Once songs are eligible for Oscar
Apparently, all the Once songs are eligible except "Say It To Me Now" (one of the ones I thought WAS eligible) because the shooting of the film actually predated the release of the albums in which the songs first appeared. The film was shot in January 2006 - WAY before it and the soundtrack were released - and the Hansard/Irglova albums with the songs on them were released later in 2006.
I'm not sure this eligibility thing is a done deal (you know how the academy can be about this), but as of now, I'm operating on the assumption that any of the songs could make it... including the centerpiece tune "Falling Slowly." So actually, a situation like this is not entirely out of the question:
Best Original Screenplay - John Carney
Best Original Song - "Falling Slowly"
Best Original Song - "If You Want Me"
Best Original Song - "When Your Mind's Made Up"
Best Picture of the Year
And "Falling Slowly" could WIN. Conceivably. That would be so cool.