Not exactly sure what the tire requirement is for winter driving but here is what I gather from both Whistler tourism site and Gov BC.
So if I'm reading them right, my all-seasons tire and tire chains are legal for me to drive on the sea to sky highway.
Any thoughts and experience driving through hwy 99 to Whistler very recently?
http://www.whistler.com/getting-here/road/conditions/
http://www2.gov.bc.ca/gov/topic.page?id=CD10049B873841338165AF1E988C4B3F