Mark's info is correct... not sure why you suspect it.

NRCan has Cdn imports by source at the bottom of this page:
http://www.nrcan.gc.ca/energy/oil-sands/18086

Their data is for 2014... US percentage has increased considerably since then. No sign of VZ oil in years.

As for Point 3, refineries are not all the same, oil is fungible. No-one who understands oil would claim otherwise. 
Mark's final point is opinion... I disagree with it.