Elvish RegrowerAffecting Opponent's Exhausts in Draft Game
My opponent had out Afterburner Expert (+1 in the graveyard) while I had my own Afterburner Expert on the field alongside my Elvish Regrower.
He was able to utilize Elvish Regrower's passive of "You may use Exhaust abilities as if they weren't exhausted once per turn" despite it not being a shared effect. This could be seen from when he used Afterburner Expert's Exhaust ability when it already had 2 +1/+1 counters on it. He had no other card able to give +1/+1 counters

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Cr4bby#41841 commented
I had same experience. I had a Camera Launcher and Elvish Refueler on the board, opponent had a Camera Launcher on there side. He activated a total of 7 times before game ended. a number of the activations were during my turn, with 1 turn were they activated it twice and another turn 3x.