My argument is that whichever party is in power, including the NDP, is limited in how far they can go. The NDP can't campaign on shutting down the oil sands.
This is independent of "the oligarchs". The NDP can't campaign on shutting down the tar sands. This is because our society is largely powered by fossil fuels. What the NDP can do in government is implement policies that decrease our reliance on fossil fuels.
For example, we have a car problem in Canada. The way to fix this isn't to propose banning cars. It is to build infrastructure and implement policies that give people better non-car alternatives.