I use Melodyne with Pro Tools - I think it does a better job TBH.

I have listened to the Little Mix performance aprox 6 times now, and can clearly pick out each line of harmony, and each of the young ladies voices. IF there is a backing track, then it is each of the young ladies singing it as I can pick out each of their voices but no other, and I can't pick out any differentiation in the pitching or breathing or note length between live and backing track, so the young ladies are singing it live exactly the same as it was sung on the backing track, which is TREMENDOUSLY difficult to do. I would therefore suggest that they don't have a lush backing track - the like of which Wand Erection had last year.

As for the whole live auto tuning thingy...that's really not my area of expertise, so I wouldn't want to comment.

It was an excellent performance.