Privilege for PR Firms
Four practices recur in guidance for PR firms on litigation: the lawyer or law firm retains the PR firm under a specific engagement letter, the PR firm keeps a summary work log without confidential detail, billing runs through the law firm, and documents are labeled as attorney-client privileged and work product. Courts have found PR communications not privileged, so none of this is a guarantee, and it is a question for the client's lawyers.
See the privilege section of Litigation PR: Best Firms, Costs and Rules.