About the same as you'd expect from any first world country: They deny any legitimacy regarding elections, petitions, or things of that matter, and may seek to actively disrupt them. They keep their troops in the area to assert rule of law and dare the rebels to throw the first punch. Seeing as these countries are typically full of people not willing to die for secession these days, nothing happens in the end.
Make no mistake, though, that if there was an organized group of Quebecois prepared to fight and die for an independent Quebec, there would be no absolutely mercy given to them. Don't let the $current_year antics fool you - Canada is perfectly willing to rip anybody a new asshole if things get serious. They'll make Montreal look like fucking Aleppo if they need to.