I discovered recently that the Pontifical Institute for Mediaeval Studies in Toronto has a Gregorian Chant Workshop.
"The PIMS Gregorian Chant Workshop meets each Saturday during term at 1:00 pm in the Laurence K. Shook Common Room of the Pontifical Institute of Mediaeval Studies. The first meeting is on Saturday, 23 September. This year, the Workshop plans to perform the mass and the offices for St Thomas Becket."
More information is available off the page.