This actually happened to me in Calgary.  I wasn't aware of it.  There was a cop 2 cars behind me.  I did a full stop.  Then turned left on red, going from a 2-way street onto a 1-way street.  I told the cops I'm not pleading ignorance as an excuse for doing it, but if they could simply advise me on the matter as to not repeat the error, as I thought I was allowed to do it as I turn left on red in downtown.  He went away and came back after talking to his partner and clarified that it's due to the fact that 1-way can turn left on red on to another 1-way, but if one of those is a 2-way, then you can't.  They let me off with a warning, which was definitely appreciated, as it was an honest mistake.