Media reports say Ontario will join Newfoundland and Labrador, Nova Scotia and Quebec in banning cellphone use while driving. (Emphasis added)

This is exactly the exception which ensures that the comma-before-and philosophy is better. I’m more than aware of the fact that natural languages aren’t defined by their precision, but there’s no reason not to attempt to root out ambiguities when they’re this easy to remove.

Let’s try this way, instead:

Media reports say Ontario will join Newfoundland and Labrador, Nova Scotia, and Quebec in banning cellphone use while driving. (Emphasis added)

Now any reader, not just Canadians, can identify that Newfoundland and Labrador is a single item, whereas Nova Scotia and Quebec are separate. Was that so hard?