It's about as safe as jackstands. Considering most people are not exactly good at doing. These guys generally have about 1000 cars in their lots and they frequently change the inventory. I rarely see anything fallen off but the 1987 grand caravan with more rust then body panels. Be smart shake it around it stays up it's good.
So far I've been to the Laval, Montreal, St-Sophie, Sherbrooke, ottawa, Gatineau and Cornwall ones. Laval sucks because of the volume of idiots without tools trying to make their first million selling whatever they bought on kijiji.
The others are generally good Cornwall tends to get newer vga cars. Sherbrooke doesnt have a lot of people so it stays cleaner. St Sophie is weird because they don't empty the cars out so you can find random shit people just left and even license plates. Gatineau is decent clean staff are a bit wack if you speak english. Ottawa and montreal are tiny not much there.