Seems that cable could be up to something as well. Virgin are trialling a new outlet box. Apparently it incorporates talkback and port switching circuitry.
The way I understood it is that the outlet box recognises when a legit modem, telephone or tv box is connected and then allows the signal to pass through. This is achieved by the talkback circuit from the connected device, as long as at least one subscribed device is attached the line will be open. This port switching circuit also has to handshake with the street cabinet so bypassing the outlet box/ connection unit won't work. Having cable but no subscription whatsoever will mean a dead/closed connection.
The extra talkback circuitry in the outlet box compares the combined talkback from the devices and any imbalance over and above a preset tolerance will close the pass through switch and raise a flag with Virgin. The talkback circuitry also encompasses a db comparator, this recognises when an unauthorised splitter or attenuator is attached to the line after install.
This means they will be able to detect the use of 3rd party equipment even when used alongside legit equipment. Also means that their cable without any form of subscription would no longer be available. Obviously this will take time to implement but they will start with the street cabinets first (guessing). This would render "inactive" lines dead, followed by new installs and then by area.
I'm not at liberty to say where I know this from at the present time.