When people stay at the line and the light goes yellow, they just sit there and nobody makes the light. If people pull up to the middle then, not only is it quicker to get through oncoming traffic, but it also means 2 or 3 people can get through on the yellow light. I don't know about the stipulations of the law, I just know common sense and what is safe. It is much safer to be in the middle of the intersection waiting for a clearing in the traffic than way back at the stop line. Back there one will need much more time to get across and thus a bigger clearing in oncoming traffic. This is not efficient and will back up the turning traffic unnecessarily.
All this being said, I have to say that I live in Quebec and the French don't drive like North Americans, they drive like Europeans: much faster, more aggressive and bend all the laws. Speeding is so prevalent here that I can go through a highway radar trap at 120 km/hr in a 100 zone and not get pulled over. Usually, one would have to be doing 25 km + over to get a ticket. In other provinces the "acceptable" speeding zone is only 10 km over. Many people here don't use their signal lights, even police. People don't do proper stops. Cars are prioritized over pedestrians (pedestrians must wait for an opening and run. Not being from here, I used to stop for pedestrians, but almost caused several accidents because drivers were caught off guard by my actions). It took a long time for me to get used to here, and it used to annoy the hell out of me, but I prefer it now. After driving in a fast, "spirited" way for so long I don't have the patience to drive slowly and carefully anymore. I know how stupid that sounds, but you would have to live it to understand. The system is backwards, but it works because everyone knows the rules....Be aggressive.