It sure looks like it was taken during the filming of BBM. The hair style and side burns is pure Ennis. But the bottom he is wearing looks different than the one in the scene with Michelle at the ranch doesn't it?
The set, from the little one can see of it, looks like it might be the Riverton apartment. In the film's final cut, we never see Ennis walking around thus attired in that setting, though. A deleted scene, perhaps?