This one wasn't especially surprising. A written plea agreement, drafted by the prosecution, states that the defendant's sentence will be 15 years. But defendant is thereafter sentenced to 15 years to life.
Defendant files a state habeas petition, which the California courts (routinely) deny. (This system really made an effort: the Court of Appeal rejected the petition with a one-sentence summary denial, as did the California Supreme Court. Impressive.) Defendant then files a federal habeas petition, and the federal magistrate -- after an evidentiary hearing -- recommends granting it. Judge Letts agrees, and grants the petition, and the state promptly appeals. (Parenthetically, this case is a good example of why the availability of federal habeas relief is important, as well as demonstrating the sharp contrast between the attention given to habeas petitions in the state versus the federal system.)
As I mentioned over a year ago, the panel opinion's treatment of the appeal was interesting. Judges Trott and Rawlinson agree with the state, and vote to reverse. While Judge Bea -- who's assuredly no liberal -- dissents, and votes to bind the state to the terms of its unambiguous written agreement.
Given this lineup, as well as the result, it's not surprising that the court decides to take the case en banc. And when it does, it's also not surprising how it comes out. It's a 9-2 decision in favor of the defendant, and binds the state to its agreement. Judges Callahan and Tallman are the only dissenters. Even conservatives such as Bybee and Kozinski are in the majority.
When someone like Judge Bea dissents in a habeas case and would find in favor of the defendant, there's a fair chance the case might well go en banc and the panel decision reversed.