While serving as president of CN, he worked to mend strained relationships with the railway's customers and partners by establishing various service agreements.
He attended McGill University Desautels Faculty of Management, the Institut Supérieur des affaires (France), and the Université du Québec à Montréal.
Before joining CN, Mongeau was a partner with Groupe Secor, a Montreal-based management consulting firm providing strategic advice to large Canadian corporations such as Bombardier and Bell Canada.
He also worked in the business development unit of Imasco Inc., a diversified holding company with subsidiaries operating in the manufacturing, retail, and financial services sectors.
[12] While on the audit committee, Mongeau helped oversee an investigation into the scandal, leading to the resignation of the CEO and the company being charged with fraud and corruption.
[13] During the audit committee investigation, the Financial Post wrote a story critical of full-time CEOs serving on the boards of directors of other companies, calling out Mongeau by name.