Informed Speculation (which has some sense about it)
HD to be introduced mid July (week beginning 8th July 2019?) on NOW TV devices, all others and BT switch on, up and running by 31 July 2019 ready for HD First Test, Ashes Cricket coverage on 1st August 2019 on all services along with terms changes.
BTTV reconfiguration in week commencing 22nd July 2019.
A poster on the BT Community has ‘got information from BT sales’ that seems to confirm this scenario. We’ll see.
Rexogamer and London Lite gave kudos