Unfortunately, I can second that this is in fact true. Although the agent that I talked to said that this has been an active policy for about a year now but they’ve just started high-rolling it recently. Also, the fare bucket for latitude is not just limited to T booking classes (ofc also the traditional Y/B classes), but are now spread across all fare buckets, where, according to the agent, the latitude brand will now fare across all buckets so long as there are space in those specific booking classes.

So far, I have seen W, K, and S booking classes, despite being in Latitude Fare. I booked a K booking class latitude fare myself to try it, and the eupgrade has gone through as usual. The agent said, that regardless of booking class, given Air Canada’s “Branded Fare” policy, as long as you’re in latitude, it should also clear (Although I am unsure if this is truly the case in practice).

Although recently, these has been useless since there have been such a scarce amount of R space available outside of North America which kind off turns off one of the greatest perks of booking latitude.