I remember one of the TekSavvy resellers mentioned somewhere on this board that Videotron doesn't allow a D3 modem on the Basic speed tier (previously 3/0.8 Mbit/s, now 5/1 Mbit/s). I think he said everything else was fine, so that should include 8/1 Mbit/s (soon 10/1.5 Mbit/s). For obvious reasons, I have no idea if they've changed that.
Strange, when I got my basic speed tier end of march I did use an docsis 3 modem. Also I think videotron would go all D3 before 2015 so this doesn't make sense besides a cash grab. Is this new? I wonder if I should worry If I move out of my Apartment I would have to buy a D2 modem just because of that.