CoreWeave did this with Ethereum in preparation for the proof-of-stake transition.

Almost all of the larger commercial miners (especially public companies) are looking at this. There are a bunch of issues (I have a conference talk last week at one of the big mining conferences on the topic, and have met with a bunch of miners on this.)

Probably long term the solution will be hybrid — mining gets done using any spare power. AI training generally requires protected power even beyond firm power and few miners have this for their mining operations, and also most of the mining facilities aren’t in the ISO 5 or 6 facilities we (I insure miners and AI) want to see for $500mm worth of mining hardware. Usually the mining companies don’t want to make the upfront capital outlay for these, so a lot of the time they do partnerships where part of their PPA is shared.