Ergo, no, you cannot. PW abilities are only on your turn, and (so far) there's no cards that change that, I'm afraid.
But the card designers, of course, know this when they design the cards. All PW abilities are designed to be used on your turn. WHat abilities are you thinking of?
Planeswalker cards would be incredibly broken if they were instant speed.
Venser + Realm Razer on an opponents turn would be LOL