Hi Andrew,
From my understanding of the canonical tag. It is used more for ensuring that google knows which URL is the one that you are wanting them to pay attention to. (To help with not having duplicate content etc)
Maybe if you investigate 301 redirects that would possibly be more what you are after. They do pass on metrics such as authority etc - but it won't be 100% of this. Moz has a pretty good article on it http://moz.com/learn/seo/redirection
Hope this helps.
