Been a dispute over this scenario in a group. Will gladly take opinions

Can Kelly criterion be used to determine wether to go all in or not in this scenario:

Hero is on the bubble of a large high-buyin poker tournament (say WSOP ME). Hero has an average chip stack. There is a raise, then a shove and a reshove by two big stacks ahead of hero who is in the BB.

We can estimate chances of winning the hand when we decide to go all in. We can estimate EV of both getting it in, and of folding. We know our own bankroll size.

Can Kelly criterion be applied to help decide if to call all-in or fold, or is Kelly criterion non-applicable in a scenario mentioned, since we're already in the tournament and that choice has been made

Could you apply the Kelly criterion in that scenario? Sure.

You would need to make assumptions about your finishing distributions in the tournament for each of the scenarios, but Kelly is certainly applicable. Instead of maximizing your tournament equity as estimated by e.g. ICM, you would instead maximize log(bankroll + ICM equity) under Kelly. That actually seems pretty straightforward to add to an ICM calculator, although the difference to normal calculations should be negligible unless the prizes are large in comparison to the remaining bankroll.