Not the same one, but basically the same crime committed elsewhere and this time with a few photos, though they could be better.

https://arstechnica.com/tech-policy/2023/02/secret-crawlspace-cryptomine-discovered-in-routine-inspection-of-ma-high-school/

You don't actually need that many computers to draw a stupid amount of power. For example if you're willing to run a Peltier cooling system... which burns ridiculous amounts of electricity to rapidly transfer heat out of the GPU and into the surrounding air (where more power will be consumed by the building's HVAC system working it's ass off to cool the room even when it's snowing outside)....

I could easily see just several mining rigs burn 20,000 watts. Run that for an entire year, and you're looking at an electricity bill running up to tens of thousands of dollars.

You wouldn't be able to draw much more than that without major upgrades that would be very difficult to do stealthily.

The description does make it sound almost like it was growing through the floors :-)

Chain of GPUs, roped down the duct?

One hell of a strange and interesting work story alright