Too late now, but I wonder if they considered district cooling, where e.g. cold water from rivers is used as an alternative to air conditioning. Seems to be used successfully in my hometown of Munich: https://www.swm.de/english/m-fernwaerme/m-fernkaelte.html
> Elsewhere, they’ve been using cool ground water to cool some of the stations. An experiment at Victoria station was the first, as water from the River Tyburn was used to cool the air in the station. This was only an experiment, but at Green Park, a permanent version was installed in 2012.
Unfortunately only a couple of stations have an appropriate water supply, and enough free vertical shaft space to fit the pipes.
There was also this, from 1938, although i don't know where they got the water:
> Elsewhere, they’ve been using cool ground water to cool some of the stations. An experiment at Victoria station was the first, as water from the River Tyburn was used to cool the air in the station. This was only an experiment, but at Green Park, a permanent version was installed in 2012.
I'd assume they did, especially if it's something that's done elsewhere.