They're trying to sell it as such, but you are correct, in many cases its not.
For instance, a number of the routes in the west end are duplicated with Mississauga Transit routes that see far more service than the TTC provides. The total amount of work that the TTC would "lose" by allowing MT to provide local service on those corridors is less than a dozen pieces of work.
The jobs start at the garages, but many pieces of work require the driver to travel on transit to a point on the route where they take over the bus from another driver.
Dan