Given the events on Parliament Hill this afternoon, I thought I would pitch in 2-Cents or so.
To me, the best/only way to "green" the tar-sands is to sell any oil from them to our American cousins exclusively, and wait for their federal and state governments to force change upon the oil patch. Harper and Co. are controlled by Western Petro interests, but to the Yankees Alberta doesn't amount to a patch of dickweed.
Indeed, Ezra, in his pre-Ethical Oil days, was touting the Northern Gateway pipe-line as our get-out-of-jail card should Obama or his successors impose green regulations: we could just sell to the Chinese or other third-world countries, who wouldn't be so picky about our carbon emissions.
Therefore, Northern Gateway is where the action is. That's the pipe that must be plugged.