Verizon, actually. Not the mail tubes specifically, but they own Empire City Subway, a 130 year old company rents out sub-street conduit for telecom. Their tubes are visible when streets are dug up for construction.

https://www.empirecitysubway.com/

https://en.wikipedia.org/wiki/Empire_City_Subway

Looks like their lowest rate (<=2.5" conduit) is $3,660/mile/yr, not including installation, permitting, and city franchising fees. Still interested?

Maybe just fill a tube container with nvme and have a few USB connected channels on the end, make a little bot to plug it into compute for each step of a processing pipeline. If you move 10T in 30s that’s like 300G/s?

Only fragments exist; they don't form complete lines anymore.

(Besides, these are 100+ year old iron tubes; there are much better things to run fiber through. NYC does not have a shortage of buried, half-forgotten infrastructure.)