Its all over the news today.
A contract was signed in 2006 to keep the GP in Montreal until 2011 but that seems to be going to hell.
F1 : Canadian organisers were not informed of decision - Montreal - F1-Live.com
autosport.com - F1 News: Canadian GP dropped from 2009 calendar
Formula One news: Canada dropped from next year's F1 calendar - GPUpdate.net Formula One