The police in Canada are saying that there is a new technique ("line-trapping") where the scammers told a lady to call the police to confirm some fraudulent details, but when she hung up and called the police, the scammers were still on the line and acted as the police. The article does not get into any technical detail.
I was unable to find anything technical about this scam online. Is this something specific to the York Police switchboard, or is it something potentially larger than this particular event? Is it even a real "new technology"?
https://www.cbc.ca/news/canada/ottawa/line-in-trapping-technology-1.5387822