I am also living in Montreal and have a permanent residency application being processed. Our application was received July 29, 2011, and I received correspondence on January 11, 2012 asking us to submit the undertaking application and notifying us that we had to send them a CSQ. If I recall correctly, this was their way of prompting us to apply for the CSQ, which we applied for immediately, and received on January 31, 2012. I believe Immigration Quebec sends them a CSQ directly, so you just keep the one they send you for your records (it's specified in one of the letters they send, so you can double check).
I also wanted to express my appreciation for the Google document maintained by Johanna...I first saw it a few weeks ago after going crazy with worry, and seeing other family's progress is such a big relief.
My timeline information is as follows if it can also be added:
We received your application to sponsor XX on July 29, 2011.
We started processing your application on September 7, 2011.
We sent you a letter on June 18, 2012 about the decision on your application. Please consider delays in mail delivery before contacting us.