I found this website www.importvehicletocanada.com and the info looks quite up to date.
I would like to add a few things
-Vehicles being imported to Canada from the US should be declared and the RIV Form 1should be completed at the port of entry. I.e. if you cross at Fort Erie you should do all the paperwork and pay any duties and taxes applicable.
-If for whatever reason you end up having to do the paperwork at an inland commercial office be ready to explain why the above situation did not happen and that your vehicle can be seized for non-report if Customs believes that you did not make a true declaration at the time of your vehicle entering Canada.
-Vehicles not driven in but transported into Canada by a bonded carrier to a bonded warehouse may complete the RIV Form 1 at the local CBSA office responsible for that warehouse. i.e. car brought up on a trailer by highway, car shipped in a marine container and then sent by rail inland.
-the process is different for New Commercial vehicle imports. To import vehicles commercially you need authorization from Transport Canada who ensure your vehicle is up to Canadian standards.
-Vehicles from other countries than the USA are inadmissible to Canada unless they are at least 15 years old or were manufactured according to north american standards and specifications. You will have to prove this with either a statement from the manufacturer or by customs verifying that your vehicle has the standards stamp/seal on the vehicle. (usually located on the inside of your vehicle door jam.
-Vehicles previously registered in Canada and then shipped overseas and returning do not have to pay duties or taxes, but be prepared to present the original bill of sale or previous canadian ownership. If you have lost both of these then contact the dealership and ask for a letter from them proving that you purchased the vehicle from them.
If you have any other questions feel free to ask.