I would say that the car IS over the line as it goes for the overtake - I've paused and stepped the video and IMHO he's over it.
To be perfectly honest, I'd most likely have ridden that road exactly the same way that Magnatom did as the pinch point came up. There's only so much looking behind you can do whilst you're trying to stay aware of the road ahead. I've had attempted passes like this (though not quite as close) - I've been aware that there's a car coming up behind, I've been checking behind but there's no way to anticipate if they'll decide that they'll try and dive past when they get closer. 99.9% of drivers will come up behind and sit and wait until you're able to safely let them get by.
Trying to work out what happens in Magnatom's video, it seems he's aware of the car and not expecting the close pass. He knows the car is there (he's been looking around and has obviously heard it behind), but thinks he's in enough of a primary position that no-one would be daft enough to try and squeeze by. Then he seems to be aware that something's happening and looks round, gets the fright of his life and automatically shoots his hand out unconsciously to fend off the danger. It's a reflex reaction that you'll see in many videos - there's a classic I've seen where a guy's almost wiped out by a rally car; the minute he realises it's upon him, he shoots his hands out to try and push it away...
Oh, and I'd love to be as perfect a cyclist as Lee. Must be nice to be able to ride every situation in such a textbook fashion (except for when it comes to stopping when the lights are at red...

) The onus was on the driver to wait until it was safe to overtake; he didn't. This is what the whole video boils down to - an idiotic cabbie endangering the lives of others.
I'll now sit and wait to be told that I should be joining Waffles & Maggers in a virtual cup of tea because I've dared to disagree...
