This is ancient history, in airport terms.

Sterile transit is, at present, only legal (other than YVR) if the passengers leave with the aircraft on which they arrived. Otherwise, under both the Immigration Act and the Customs Act the carrier is obliged to present the passengers for inspection.

Since AF's 747's do not fly on to St.-Pierre, this phenomenon is long since dead.

It doesn't matter if the routing is domestic, if it uses an international transit point, it turns into an international flight under the Warsaw Convention.