Sorry TF, missed that question.
We used to have an east side nestbox but we had high fledgling mortality from it - the chicks would take their first flights and end up hitting the buildings or dropping into traffic at Portage and Main. Keep in mind that it takes a couple of weeks befor the chicks are half-way decent flyers - the first week or so they are just neat looking gliders, no up capability and way too much down potential. So we removed the east side box back in the 1990s. It was located where the spycam is now. With the westside box, the chicks' first flights end up west of the building where there are buildings with big roofs - the MTS Centre (as did the old Eaton's Building), Portage Place, the Convention Centre and The Bay . Also, the majority of the buildings to the west than to the east, so the chicks have more chances to stay above the traffic and not get caught in the "canyons" formed by the taller buildings to the east. Doesn't mean they don't end up in traffic from the east, just way less often and with a fraction of the injures (serious and otherwise) and deaths.