While everyone know that a negative review in Google raises lot of apprehensions as the businesses invest lot of time and effort in SEO to make the page listed in the priority pages: They would not like to have a false negative review to hamper the reputation of the business.
If a review is placed in Google which is false and is been written just to defame or compete the company, here are the things you can do
New account: Most likely, the fake reviews will be written with new account and fake names, in this case you can flag the review as inappropriate and ask Google to remove the same: Its easy
Old account: When the intruder go one step beyond to use his old email account to post the review(which again you believe is untrue) , you can actually use this to your advantage by posting a reply : your reply should be humble, on the point ask the whereabouts of the service the review is unhappy about , also mention that if you further did not get a reply , it will be treated as a PR strategy of a competitor and will be taken sportingly and as a healthy competition and you are happy that you are a potential threat to the competitors in the business;
Don’t use abusive and uncalled words in your reply: It should elevate your value and the potential clients like you even more