Then they should go ahead and meet him. Oppo leaders often meet people the premier won't, as they typically have more time on their hands than the premier. It would be a lovely opportunity for a photo-op with the mayor. I'm sure Tim Hudak would like more pictures of him and Rob Ford together; I'm sure Andrea Horwath would like a few more too.
PS. I'm a T.O. resident and I'm fine if Premier Wynne would rather deal with someone else rather than the mayor. What good would a meeting do other than further the man's re-election plans?