I suspect the new boundary is for additional space for construction trailers etc on the north side. They had them on the south side but moved them when truck traffic was hindered. I think they are temporarily inside the low rise portion of the former Toronto Star garage.
They are utilizing the south grade level for deliveries of rebar and concrete and waterproofing materials needed at this stage and within the boom reach of the single crane.
Likely it’s an effiency effort with the site resources they have right now.
The othe pic, between the gardiner and the rail tracks shows a yellow pipe device. Several times this week they have let compressed air release from this. I think it’s a pressure test of underground services, likely sewer, I’m guessing so if anyone can confirm or correct that’d be great.