A lot of that map is explained by oil: https://www.spec2000.net/text100fp/cdnoilmap.jpg

In the last couple decades, it's become affordable to mine tarsands. The oil boom has meant people in those places make a lot more money. Naturally, they are making more money than their parents did.

The other green area is Toronto. If you're 40-50 in Toronto today, you probably bought a house in your late 20s or early 30s, which has now quadrupled on value.

All of that to say, many of the places where mobility is rising may be short lived. In reality, we may be an entire country of low mobility, except for the few lucky areas.