It appears that he only uses to e-brake to break the tires free of traction. I honestly didn't know it was done this way, thought it was just the dumping of the clutch to break free.
There are different techniques. They usually have crazy power to break the tires loose on a whim, but 'powering over' is only one method, and AFAIK is more used to control the car during mid-drift.
Initiation requires weight transfer; the e-brake helps to encourage this. There's no ratchet/locking mech on their brake handle. It's basically just a primitive way to give some independent control over front/rear braking, like you'd have on a bike.
I liked the vid. Not the absolute 'prettiest' driving I've seen, but I can respect that it seemed unrehearsed and he was really getting on it; maximum speed rather than maximum sideways.
WRC it a totally different animal, as the 'drifting' is simply a result of trying to go as fast as possible in a low-traction environment. They're not trying to co around a turn sideways so much as they're trying not to smash into a tree and die.