The plant pictured in the OP is a beautiful hybrid cultivar of a Bearded Iris (Iris x germanica cv.).
While lovely, its appearance is within the normal range of variation for hybrid Bearded Iris.
While Bearded Iris may often long persist as garden waifs, they are not a wild or native plants in Canada.
All Rhizomatous Bearded Iris (Iris, Subgenus Iris, Section Iris) are native to Europe, Asia, northern Africa or Mediterranean islands.
The general color pattern of this Iris is known as 'Amoena' (white or pale standards with darker falls).
There are several old cultivars: Iris x 'Mrs. Andrist' (1919) and Iris x 'Rhein Nixe' (1910) which look a little like the Iris pictured above.
Of course there are many other similar cultivars of which I am unaware.