As of March 16, 2020:
To reduce the spread of COVID-19, Canadian President Justin Trudeau has closed the border with the US. They will allow US citizens and those shipping goods into Canada to access the country. Truck drivers, train and air crews are exempt from the closure.
“We believe the risk of essential workers crossing the border can be managed effectively,” he said. “For the purposes of not just their own employment but also to keep Canada moving, essential workers need to be able to keep moving across the border.”
Further updates may be found at the Canadian Trucking Alliance website: http://cantruck.ca/covid-19/