Believe it gets sent to Kennedy first. If 4 justices want to hear it, it is tradition to grant the appeal. That being said, I bet there are only three votes there: Scalia, Thomas...and maybe Rehnquist. Rehnquist hates Congress treading on 'his' turf, i.e. might kill Terri to protect the judicial lords.
Keep in mind that in Cruzan Scalia said judges have no business interjecting themselves into life and death decision.