Apparently the MI-17 was climbing fast to avoid AA fire, if the TCAS wasn't working or the helicopter didn't have a transponder (probable seeing as it is a military aircraft but I don't know anything about that).
I'm pretty sure that even if they do carry one, it's not actually turned on while actively engaging in warfare, as you wouldn't want to draw the enemy's AA fire to you. TCAS was hence most likely out of the question and only see and avoid could have prevented the collision.