Hi Jim,
I got turned on to Mary Margaret O'Hara a few years back. I know she lives in the west end of Toronto, and she rarely performs live, and when she does it's usually to back up another musician. She will occasionally do a few songs at a show with multiple artists.
About two months ago, my friend let me know that she was playing a solo show in the city. To be honest, it's one of her first solo shows in a good few years I would say. Unfortunately I was out of town, or I would have been there for sure!
She is very well known among musicians here, and she sang some backup on Justin Rutledge's last album. I know she has a rabid following in the UK, and I forget which UK magazine it was, but they rated "Miss America" as one of the top ten albums ever (!). She is a tremendous talent, but I believe she has mental health issues which can impact her ability to work.
I really love that album, it is very unique and her voice is classic Irish awesomeness.