they're quite common in brazil and spain (on the most touristic / surf beaches) - some times operated by companies, other times by the city hall itself

I'm guessing you aren't talking about Rio. I live in the Zona Sul and haven't come across lockers on the beach (though I had the idea literally a few days ago). If they do exist here, whereabouts can I see them?

I remember seeing some in Paraty... Didn't see any in Rio indeed (only those "refreshment units" that spray water on your face :-))

Dono what part of Canada you've been to, but they are all over the place in Toronto.