I always assumed it was ok to turn left if there is more than one lane. People turning right have their own lane, you have yours. Obviously if there is not enough space, they have a bigger car, they drive too fast - I don't do it. It might fly somewhere outside of GTA on quiet streets but here you'll get the horn and road rage if you take too long to make a turn.
Same kind of thing with people making a right turn pulling out of the plaza. You're turning right onto a big multi lane road. If the closest lane to you has no cars in it - go ahead and make a turn slowly. I see some sit for a few minutes until the road has 0 cars in all of the lanes, then they turn right.