Just browsing the CRA website as well, when you make the change, there is a deemed disposition, which will result in a taxable capital gain. What you can do, is attach a letter (no form) electing to defer the gain under 45(2). You'll have to report the rental income (of course), but cannot claim CCA on the property.
This link goes over changes in use:
http://www.cra-arc.gc.ca/tax/individ...es/menu-e.html
This one goes over changes from personal use to rental property:
http://www.cra-arc.gc.ca/tax/individ...gingall-e.html
Hope that helps a bit - I haven't done too many returns w/ rental income.