Police warn of new “line trapping” scam

This has been going around for a while, but I have been unable to find anything technical about this scam. Does anyone know how it works, or a link that explains it?

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"?

It seems rather incredulous to me that every article says the same non-technical blah, and they all lead back to one story about this one person, while no technical information or even hints about it appear outside of that rather tiny bubble.