Of the Canadian oil being imported by the U.S., approx. one-third is blended bitumen. More is included in the heavy oil fraction.
Approx. 30 percent of U.S. oil imports comes from Canada.

In other words, of the petroleum in pipelines from Canada, a fair amount is from the oil sands of Alberta.

See 2012 Q3 Est. Canadian Crude Oil Exports by Trpe and Destination.
http://www.neb-one.gc.ca/clf-nsi/mrgynfmtn/sttstc/crdlndp
Also see www.eia.gov figures