Its clearly a case of black ice, i've driven through it enough times to recognize when it is the culprit. Even harder when its patchy (such as in the vid) since front tyres might grip while rears will slide, then they catch and fronts have no grip and all kinds of different situations.
One day we had solid freezing rain overnight, next morning going to work i didnt want to leave my car, its a wicked rush trying to keep the car pointing in the right direction and taking corners has never taken so much concentration and work :P, even going at 5 km\h if you brake, you'll slide for at least 10 meters without any sign of slowing down.