Well, I don't think we can judge the vocals based on how they sound unless they sound pristine, because they could very well have taped her during rehearsals and played that back. That way with a few run-throughs there are enough takes and time to get it to sound live and correct enough.
I actually worked on the last one and forgot to ask how they went about it all, though I'm sure I probably wouldn't have been told it was playback even if it was.