What an odd thing to do! The main draw for BT Mobile when I used it about 2 years ago was the discount for taking all the services together but mostly having everything on one bill, Direct Debit, etc.
Making you go to EE for your mobile, especially when it’s effectively the same company seems really silly, even if they do manage to cobble together some cross-party discount.
My assumption sits firmly with this being the beginning of one service to do all the things.
Hopefully this means Zevvle will see 5G 
That’s the one! Didn’t know this was public 
So Transatel = China telecom?
Also whoop for WiFi calling.
Seems it depends on the contract. I’m interested in 4G calling. I’ve been caught out a few times where I’ve had a good 4G signal, no 3G signal, calls getting being done in 2G, but the mobile data on 2G being too slow to do anything useful with, yet needing it on the call.
More were really getting off topic for this thread…
Line rental? 
cost of maintenance for towers etc