The police services building next door is not a station. There is no 'muster' that could take place on Fort York grounds. One cannot go to that building for any form of police response - one would be directed to the Fourteen Division station on Dovercourt Road.
The building immediately to the south of the Liberty Market Tower is the police vehicle service centre. The shop performs all the police vehicle regular vehicle maintenance and repairs, along with commissioning (installation of radio, radar, computer and other related equipment necessary for police operations) for a newly arrived vehicle and decommissioning (removal of such equipment) when a vehicle is being retired and disposed.
Obviously, none of these activities need to be conducted in the core of the city - a more remote location would probably be eminently feasible. But, to repeat the point - this is not a traditional 'cop shop', and mustering at Fort York, even on an interim basis, would not be a workable solution to the vehicle service centre's needs.