CBC just posted this investigation in their website https://www.cbc.ca/news/canada/cra-phone-tax-scam-marketplace-1.4830141
"You've probably got the call: An automated message threatens you with arrest over unpaid taxes. Call back and you'll be further threatened by someone claiming to be an agent of Canada Revenue Agency.
They may demand as little as $700 — though some have handed over more than $100,000.
At least 60,000 Canadians have complained about being targeted by the phone scam over the past five years. More than $10 million dollars has been stolen in that same time period, making it one of the largest cyberscams in Canadian history.
Be aware of the scam, and don't spend your time and money with them.