I'm confused now as well!
Several years ago they tried to install a smart meter despite me saying we have no mobile signal. The guy who came said it wasn't a problem because he had lots of ways round that. 5 hours later he admitted defeat and put the old meter back in.
Then three years ago Octopus fitted one, they said it didn't use the mobile network and it works. I've looked in the meter box and the transmitter has two lights which the BBC article, extract below, says denotes the Northern type.
As a rule of thumb, smart meters in the northern region designed to connect to the radio signal have two small indicator lights on the communications hub, fitted to the top of the smart meter. The hubs fitted to smart meters in central and southern regions, receiving the cellular signal, usually have five of these indicator lights.
If they switch it off we will be unable to use our smart tariff unless they can link it to wifi.