I am not sure but from personally reading it I just assumed that they were paying for the power. It is just that maybe the regulations against using that power for marijuana vs crypto currency might be different. I have not personally checked this but I am imagining that you could spend extra power for such things and just pay for it but there is possibly an energy cap against those mining bitcoin and you may get charged extra. I'm not 100% on that but that is my assumption I got from this article.