This looks like quite a challenging site from geotech perspective - deep excavation, adjacent structures, no bedrock, weak-looking soil. Looks like they're reinforcing the bottom of the excavation in advance of pouring a massive raft slab.
View of more than half the building is obstructed by Jade, I think they were working on that side mostly.
The NW side of the building (facing Lake Shore on the right of the photo above) is at its final height of three stories. Initially it was supposed to be an above-ground parking lot...
501 currently runs as buses west of Roncesvalles till December or January. They will be re-building tracks and adding a separated bike lane on Lake Shore from May till December.
There is a transportation master plan underway in the area, so implementation of traffic / transportation...