Yes, I have been a part of management consulting firm in merger and acquisition process. And that was a failed process. What my experience says that it got failed because managers do not pay enough attention to the strategy, proper implementation of the acquisition process and business activities after the transaction. Business consultants have the significant role in M&A processes and their knowledge is very important for transaction process. They play an important role in preparation of documents related to the transaction in conjunction with top management and lawyers. The nature of possible interventions in transaction varies depending on the specific task that is in front of consultant, the goals of merger or acquisition, and the time (phase) when the consultant came in the process. Consultant's job in mergers and acquisitions is taking place in several phases and that are planning prior to the transaction, the integration plan and implementation and in the end, evaluation of transaction and activities after the transaction. http://investmentbank.com/mergers-and-acquisitions/
