No, no no.
If the car is over 15 years old, you still have to e-mail or fax your title to us export. You still have to stop at us export before crossing the border. You still have to go to canadian customs and fill out the RIV form 1. Except on that form, you check off [exempt - Over 15 years old.]
You DO still pay the RIV fee.
You DO still pay taxes.
You DO still pay the A/C tax.
Regarding plates in the USA: You can obtain temp plates from (almost) every state. Temp plates are ONLY valid in the state you are in. (If you buy a car in NC, get temp plates there, and get pulled over in NY, you have invalid plates.)
I wouldn't worry about plates too much. I've been pulled over in some ridiculous situations in the USA without valid plates, never had a problem. DO make sure you have insurance though. Your insurance company can usually suggest what they'd like you to do plate wise. Mine told me to stop in EVERY STATE and get a temp permit. No, thanks