You know, i've never heard of this in Montreal. In fact, i've seriously never heard of this at all.
Just out of curiousity, i'm going to call our SPCA, rescue center and go to the pet shops around here and inquire if they do this or not. I'd be very interested in finding out.
I'm assuming this has to do with Halloween.
What do people do, adopt a black cat just for Halloween and then want nothing more to do with it after that? Please don't tell me they do any harm to the cats.