Depending on when you enroll, you'll be given the choice to do your BMQ either full-time during summer, or part-time starting on September. Depending on your trade, I believe they are all full-time during the summer and must be completed inside 24 months from the date you get enrolled.
IE: I enrolled at the end of March; I was given the possibility to either sign up for the next BMQ in the end of May, the 2nd one in June and Part-Time in September during weekends. I chose to be on all 3 lists in the event that all places are already filled up.
My trade's course will be this summer from the end of June until Mid-August. My whole summer will be dedicated on training but after that is done, you're free to attend your unit when possible with your civilian life obligations.