Steve V suggests that Jack Layton and Stephane Dion put together a "high-profile, extensive meeting" to work on the environmental issues which figure to dominate the upcoming sitting of Parliament. And in principle, the idea is definitely worth putting into practice, or even expanding if possible. After all, an opposition summit - either between Layton and Dion alone, or including Duceppe and/or May as well - could both facilitate the development of a consensus policy, and ensure that the Cons then can't get away with anything less.
That said, I'm far from sure that such a meeting is likely to happen. After all, Layton and Dion have already met to discuss the subject among others - which was followed by Dion calling the review of the Clean Air Act a "game" and resolving to "denounce" it. Which unfortunately signals that it'll take somewhat of a loss of face for Dion to now agree to work with Layton...and creates a real risk that contrary to Dion's own admonition that the issue of climate change shouldn't be a partisan one, politics will win out over the upside of cooperation.