Can Bounty Hunter be activated during a teammate's turn in 2v2 to give units ganking?

Ruling: No, Bounty Hunter cannot be activated during a teammate's turn. Only reactions can be played during other players' turns (with the exception of spells in 2v2, and actions during showdowns).

Nuances:

• Spells can be played during a teammate's turn in 2v2
• Actions can be used during any player's turn when there is a showdown
• Bounty Hunter is neither a reaction nor an action, so these exceptions don't apply