The general rule is if you are a Canadian citizen or PR, you are not allowed to drive a car with US license plate from the US to enter Canada, UNLESS, you can prove that you are physically living in the US.
At that time I was working in the US with H1b, I think they treat that together with my US driver's license as an obvious prove and I was working and living in the US. So, I never had any problem driving either the US rental car or my own car with US plate to enter Canada.
So, I think as a H1b holder you should be fine. And I guess, if you have B1/B2 visa and driving an US plate car, there may be an problem - no real experience though.
At that time I was working in the US with H1b, I think they treat that together with my US driver's license as an obvious prove and I was working and living in the US. So, I never had any problem driving either the US rental car or my own car with US plate to enter Canada.
So, I think as a H1b holder you should be fine. And I guess, if you have B1/B2 visa and driving an US plate car, there may be an problem - no real experience though.