The search giant had a similar issue in the U.S. in September, prompting them to temporarily ban rehab-related ads. Google has, on occasion, penalized companies for using "black-hat S.E.O.," but has never acknowledged boosting reputable sites in order to combat deceptive companies.
However, according to the article, three S.E.O. experts say that is likely the case in this instance, with government-sponsored rehab sites dominating top results.