I haven't studiesd these things in any detail, but I think there might be some 'chalk and cheese' going on ....... In 2016, it was reported that over 1.6 million teleswitches were in use. .... The Radio Teleswitch Service is broadcast alongside the longwave output of BBC Radio 4 from the Droitwich Transmitting Station..... In 2016 ....... While most suppliers acknowledged the system could ultimately be replaced by smart meter functionality,
The "Radio Teleswitch Service" is (technologically) very trivial. The signals are simply broadcast by the BBC, using a frequency with very good coverage. Any/all 'receivers' ('teleswitches') can listyen to that signal, and it makes no difference to 'the system' as to whether there are 20 teleswitches or 20 million teleswitches 'listening'.
I may be wrong, but I think that SMETs requires all communications with 'smart' meters to utilise secure handshaking. If that is the case, then communicating, separately, with each of 20+ million meters would be an almost astronomically greater exercise than 'broadcasting to the world'!
Kind Regards, John