Went to a camping in the Laurentians in Québec (Ste-Agathe) and there were those things near some camp sites. The sites are only accessible by footpaths. No car access. And if you bring a bike, you have to walk it up a hill, so I doubt they are bike racks.
EDIT: I have sent an email to the park and they have been kind enough to reply. It's just a type of fireplace with a grate. They didn't give more info than just this. Thanks to everyone for pitching in!
I don't think it's worth the cross-post. I'm from the region, go camping several times a year and never seen something like this. The camping is on the route of my bike trip between Montreal and the Mont-Tremblant SEPAQ, so I may go back this fall and ask them. Or maybe next spring.