The defence of qualified privilege holds that an otherwise defamatory communication can be justified if it is a “responsible communication on a matter of public interest” and: 1) the publication is on a matter of public interest; and 2) the publication was responsible, in that the defendant was diligent in trying to verify the allegations having regard to all the relevant circumstances. Where these two elements are present, a defence will be available, even if what is published is false (see Grant v. Torstar Corp., 2009 SCC 61).
Historically comments to media, or even in the presence of the media, are not granted such broad protection (see Jones v. Bennett  S.C.R. 277) but it may be the Mayor of Toronto has a defence if he can show (and it is up to him to show) he fits within the broad definition of qualified privilege:
Mayor Rob Ford’s legal team argues that comments he made about corruption at city hall during the 2010 campaign were made in the public’s interest and that politicians must be allowed to speak freely on controversial issues.
This is the backbone of Ford’s defence in the $6 million libel case which began Tuesday. The suit was brought against Ford two years ago by restaurateur George Foulidis, whose family runs the Boardwalk Pub in the Beach.