Good to see that there's some other people that are in our shoes. I hope this info helps them.
My partner was on a study visa, so we didn't need to change our plates when we brought our car into Canada/BC a few years back. It has Colorado insurance and plates.
In June we got PR and were worried about what to do.
Went to a local CBSA office yesterday and they said no worries and handed us a Form 1 and said we could keep driving the car and go through importation the process.
The problem is a classic Catch-22. We could import the car to Canada without going to the US, but then if we drove the car back to the US ever again it could be seized. And while we could technically cross the border, we'd be exposing ourselves to much higher COVID rates in Washington, and we'd have to quarantine for two weeks upon return. Blaine's import office was inflexible: they require us to be in the USA for 72 hours to export the car, and as the other poster says, a car import isn't "essential travel" from Canada's side.
So today we went back to the CBSA office and explained the situation and the officer said, "Don't worry about it. As long as your car is insured you can have it here with US plates until the border opens to non-essential traffic."
This is in line with this part of the CBSA site about COVID Info for Canadians and Permanent Residents:
https://www.cbsa-asfc.gc.ca/services/covid/canadians-canadiens-eng.html
Temporary import of US-plated vehicles into Canada
Until further notice, the CBSA is lifting the 60-day condition regarding the temporary import of US-plated vehicles by Canadian residents. A new deadline for when these vehicles will need to be exported or permanently imported with applicable duties and tax will follow.
Hopefully this helps any folks out there in a similar predicament.