(27 Feb 2023, 1:59 pm)Adrian wrote EE users, and users of any virtual operators that use their network, have been able to get 4G/5G in the central section tunnels for a while now. It works perfectly from my experience.
I thought it'd have been a partnership, but it was pointed out to me that it was installed and is maintained commercially by EE. At least the proof of concept is there now, if any other operators decide to do the same.
Should be easy enough to do, even the London Underground has phone signal in the stations now and they're a warren of tunnels compared to the Metro which is pretty simple in comparison.