In the 2021 dataset, the 4 CMAs that share a provincial border between 2 provinces (for example GeoUID 505 and its sub-parts 35505 (Ontario part) and 24505 (Quebec part)) all have the same Population values while, I think, we can actually get their respectives (sub) values in StatCan, am I mistaking?
For info, the 4 CMAs in question are Campbellton(GeoUID 330), Hawkesbury (GeoUID 502), Lloydminster (GeoUID 840), and Ottawa - Gatineau (GeoUID 505).