As far as I know, the only tax loss season in Canada is late in the year, just like in the US. Only difference is that in Canada, the last day to sell is Christmas Eve, while in the US, it's New Year's Eve. Revenue Canada uses the settlement date, rather than the sell date.

In the US, there's considerable tax inefficiency in a lot of mutual funds, so they need to sell their losers by their particular year end - often Oct 31. This is one of the reasons the third quarter is often weak, and why important bottoms frequently occur in Oct.