If you fly from the US into Canada, ATC or FSS likely can tell you the adjacent Canadian ATC frequency you need to talk to.

See below for NavCanada FISE:

http://www.navcanada.ca/EN/products-...tives-rco.aspx

Unfortunately Canada has Class B over 12,500 in low level airways and terminal areas which requires a clearance. Close to the border, Class B holes are few and far between.