Well let's just start off by saying that I have my share of traffic tickets, and I fought them all, and I have lost in all cases. I brought witnesses that were in the car with me, I took pictures, it did not matter. I live in New York City. Population 8 million. I don't know how many people take the public transportation in Toronto, but we have 4 times the number of people here, so I'll just assume that my traffic conditions are far worse than yours.
That being said, there were other people who were already in the left lane. Answer me this: how did these people get in that lane? Why was Dave not able to get in the same exact lane that was occupied by other motorists around him. What possible reason does he have not being able to merge for, what is it, 400 feet? Let me try to assume this: he was riding past all that bumper-to-bumper traffic hoping to see an opening. Well he did not see one until he got to the solid white line when people assumed nobody was arrogant enough to cross it in front of them. He can blame construction and sun glare, pesky pedestrians, etc. But the bottom line is: the other people managed to get in there because they put on a turn signal, waited for an opening, and changed into left lane in anticipation of making a left.
At first I could've given you some slack, thinking maybe you are from US and driving there, not knowing the local streets, but that isn't even the case.