In message , at 12:27:14 on
Tue, 30 Jul 2019, Jarle Hammen Knudsen remarked:
"Transport for London confirmed to the Guardian that 4G mobile
phone technology would go live in tunnels on most of the Jubilee
line from March 2020 and on other lines in the coming years."

Wouldn't it be more forward-thinking to go for 5G?

No, because the emergency services contract (which this is piggy-backed
upon) is 4G.
--
Roland Perry