State immunity — Jurisdictional immunity — State corporations — Immunity of government controlled corporation — Corporation established by government of Quebec for development of hydroelectric resources — Corporation’s operations completely controlled by government — Fatal accident — Widow’s action to claim damages — Whether corporation entitled to sovereign immunity — Whether actions purely private or of a commercial nature — Restrictive theory of sovereign immunity — James Bay Region Development Act RSQ 1977 and the Hydro-Québec Act RSQ 1977 — The law of Canada