Obviously, this has nothing to do with your outs. What you do need to do is define is exactly what you are wondering about. Is it two pairs of 9s vs two pairs of 8s? Or is it any pairs? Also, do you want to know how likely to happen in one hand, or how likely to happen ever. Also, all four of them need to get all-in, which in any normal game probably isn't going to happen (late stages of a tournament, maybe).
That all said, I don't really know the answer. I'm sure that someone will be able to figure it out, but I would say that it probably won't help you much to know the exact probability.
As the cards were dealt from a shuffled deck, aren't the odds of those cards falling the way they did exactly the same as them falling in any other way?
