I happened to find that Canadian Catholic Conference held in Ottawa, Ont., 1972 approved the "A Mighty Fortress Is Our God" (originally written in German with the title "Ein feste Burg ist unser Gott") in their Catholic Book of Worship and that it was included in a list of suggested hymns in "Cantica NOVA Publications" in the States. 

My paternal grandmother would feel happy to have known that, because her grandson is allowed by the grace of God to sing the hymn at Mass in the Roman rite that she surely loved singing, though she belonged to the Reformed Church.

I really love the hymn!