Sabia held a number of senior positions in Canada's federal public service during the 1980s and early 1990s, including Deputy Secretary to the Cabinet of the Privy Council Office. Sabia's supervisor at that time, Clerk of the Privy Council Paul Tellier, left the public service in the early 1990s to assume the presidency of a Crown corporation, Canadian National Railway. He subsequently persuaded Sabia to follow him to help in privatizing the company. Sabia held a number of executive positions at Canadian National Railway during the 1990s, including the position of chief financial officer.