When the 9th Bishop of Moosonee, Tom Corston, retired on December 31, 2013, the Diocese of Moosonee was reorganized as a mission area of the Province of Ontario, with Johnson, as metropolitan, serving as bishop of Moosonee in addition to his jurisdiction in the Diocese of Toronto.
On December 31, 2013, Bishop Tom Corston, the 9th of Moosonee, retired, and the Diocese of Moosonee was reorganized as a mission area within the Province of Ontario. Johnson, serving as metropolitan, became the bishop of Moosonee in addition to his responsibilities in the Diocese of Toronto.