Same goes for people using verlan. Quebec French is not to be reduced to a level of language: it has certain distinguishing features about its vocabulary, grammar, tonic accentuation (stress) and accent. It's the same for all "varieties" (I lack a better word) of French around the world: familiar and/or very colloquial use of a language is hard to pick to people not accustomed to it. Correct and litterary Quebec French levels are very understandable by whomever interested.

Now, the reason why I can get verlan, or very different accents (let's say the haitian one: not that I'm saying Haiti French is to be compared to verlan, it's just an example here), is because I've been exposed to them. If you don't show any interest in any other French cultures, you won't be able to understand anything that differs from yours. Montreal is a pretty cool city to get in contact with a broad range of different French accents.