Given that central banks are among those slowest to adopt new and efficient technology (magnetic tape and paper documentation is still how most banks globally operate), and are guilty of the most inefficient and bloated structures and wasteful practices, I'd be very surprised if they were able to provide the most efficient energy usage were they to go into mining.

So aside from the political reasons why "CBM" won't be a cure -- they have to accept they're not even viable for consideration.