[officedweller]

If you place the switch to the east of the SkyBridge approach, it cuts the cost hugely and you just need the one track under Clarkson St.

The new station platform can also be between Fourth St. and Blackwood (less interference with the condo towers to the north of the station) - with a short connecting passage to the Columbia platforms/mezzanine.

Are the two buildings at Blackwood and Clarkson (the rectangular ones) residential or warehouses? Seems like the south one could be expropiated to provide access to the apartment building during cut and cover of Clarkson.