I really don't get it.
First the city has no power itself, the deal is with an electric company that provides energy there.
It is called Looop and it specializes in renewable energy.
But, and there is a big BUT
https://news.bitcoin.com/japanese-renewable-energy-provider-low-flat-rate-electricity-crypto-miners/Looop explained that customers can sign up for a “1kW equivalent contract (10A or 1kVA)” which allows usage of up to 250kWh for a fixed monthly price of 6,170 yen. They can also sign up for multiple contracts. For example, a 3kW contract will allow them to use up to 750kWh. Overages are charged at the rate of 22 yen per 1kWh.
250 kWh at 6170 yen means 55$ and that would still be a gigantic 22 cents per KW.
There is no way you can mine at this prices.
Somebody messed up the numbers really bad.
If this is all they can offer to consumers in a "promo" who is going to pay the subsidies for that mining operation?