<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Tried to check YYZ--LAS fares on the website today after the email from AC about their fare sale. Lowest fare I could find was $592 including all taxes and fees, and I tried several date combinations in October.</font>
YYZ-LAS is a very popular route. With the lowest fare requiring only a 2 days stay and not even a Sat night stay, it is not surprising to see that the flights being full. In fact, this route got one of the lowest V fare for long haul NA flights. This seat sale is in Q class and ITN shows that most days does not have availability in Oct.
I tried Oct 8 - Oct 10 and got $463.32 CAD with Q class available both ways. So ITN & expedia is your best friend when attempting to use AC's website to get the lowest fare!