The Leslie Street carbarns are scheduled to be ready by summer (September?) of 2015. There is a capacity for 100 new streetcars.
A new streetcar is about 30 m in length. In comparison, a regular length bus is about 12 m in length, while an articulated bus is about 18 m.
I am guessing that Toronto will not have 100 new streetcars on hand or available by the time the Leslie Street carbarns open for use. So, in the meantime, while we wait (and wait, and wait) there would be room available to house buses, until a new bus garage is built (or at least paved) or the remaining new streetcars arrive and displace the buses.
The remaining new streetcars would be distributed between Roncesvalles and Russell.