Yes, and it's way better than jugs and cartons. In eastern Canada, it's the primary way milk is sold. You can buy cartons if you only need a small amount, but 4L jugs are only available at a few convenience stores and are not sold in grocery stores.

A larger bag contains three 1.33 L sealed, transparent bags of milk (4L total). Pop the bag into a jug (special jugs are sold for this, but any old jug will work) and cut one corner off to pour it. Minimal waste, super easy to pour, no lid required, doesn't take up so much room in the fridge, doesn't take up so much room on the dinner table... what's not to love?

Yes, not all of Canada, but definitely in Ontario:

[0] https://www.youtube.com/watch?v=VTPgd4HUk4w

[1] https://www.thestar.com/news/ontario/2010/02/04/so_we_drink_...

And, as for the paper/cardboard thingies, the website is up on them too and is eagerly monitoring the developing situation:

[2] http://www.horg.com/horg/?page_id=2936