if you want a formal decision from CRA you need to fill out a residency determination form.
http://www.cra-arc.gc.ca/E/pbg/tf/nr73/README.html
it will take 30-45 days to get a response but it is the only way you will get a concrete answer. The agents on the phones will tell you to fill out the form if you want a concrete answer rather than a general one.
If you are actually a non-resident of Canada you will only have to file a tax return if you have no Canadian sourced income in a given year.
Be careful with using the word deemed as well. A deemed non-resident is not the same as a non-resident.
You also cannot be a resident of 2 countries at the same time. So if the US considers you a resident for tax purposes you most likely will be determined to be a non-resident in Canada. But like I said, if you want a concrete answer fill out the NR73 I linked to above and send it in to the CRA.