If I {Act of Treason} my opponents {Hangarback Walker} and sacrifice it, I keep the tokens, correct?
Yes you do.
109.5. (http://imtgapp.com/forum/index.php?action=imtg;area=rule;number=109.5.): For a triggered ability, this is the controller of the object when the ability triggered, unless it's a delayed triggered ability.
nice, thank you. I'll always be happy when an opponent play their Hangarbacks now!