Olympics 2012 track cycling

What counts as a completed change? First rider completely swung up out of the way? Completely passed? Front wheel of second rider in front? If the front rider swings up but their front wheel is still ahead by the mark is it still complete?

I can see why people get confused!

Exactly. The rules simply use the term 'draw away' this doesn't say in which direction.
Simply put though, the lead rider needs to be out of the way of the other before that last 15m point. Not sure the dynamics of the race /track geometry would actually allow the lead rider to still be ahead if they'd swung right up...unless he/she was still hammering it and rider 2 was suddenly a bit slow