"....But if Ottawa doesn't get the environmental protections it wants, it won't be a deal breaker..."
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Which if you think about it, calls into question the Liberals stance on the environment.

If they are not willing to walk (if they don't get their demands included), just how committed are they to this? 

This is another one of those items that has nothing to do with the item itself (like say, electoral reform), and everything to do with the Liberals keeping their word/promise..