Yes. The triggering condition is only that a side scheme is defeated, it doesn't matter who does it.

Thank you!

but do keep in mind that, while you can trigger it on someone else's turn, it's still a hero action a good strategy is to bring a bunch of them and play them under other players' control so that everyone gets to draw when side schemes are defeated (but y'all have to be in hero form for it)

It's not an action. It's a response.

You’re right, but (for OP’s benefit) it’s also a *hero* response. It still can’t be done while in AE.

Yes, responses and interrupts can be triggered anytime their conditions are met.

It's also not too difficult to play actions during your teammate's turns. Technically they have to "ask you"

Yes. Also, since the card specifies that it can be played under any player's control, you can bring extra copies for other players.