UPDATE - US broadens Freddie Mac probe to Wall Street role Tuesday November 18, 10:33 am ET (Adds details, background) WASHINGTON, Nov 18 (Reuters) - A U.S. financial regulator is investigating the role of companies that were counterparties to questionable deals at the core of accounting irregularities at mortgage finance company Freddie Mac (NYSE:FRE - News), an official said on Tuesday. "We are in the process of reviewing the counterparties' roles in transactions relevant to our investigation," a spokeswoman for the Office of Federal Housing Enterprise Oversight, Corinne Russell, said. Russell said the agency has a wide range of actions...