There's a disconnect here.
Toronto pays for a police service but does not make the laws (or at least the major laws) that the police must follow.
So calling Toronto a Sanctuary City does nothing. It's as if Toronto said "no drug prosecutions of any sort"; good idea or bad it's not within the City's power to decide.
http://www.thestar.com/news/investigations/2015/11/24/toronto-police-urged-to-stop-immigration-status-checks.html Despite "Sanctuary City" status, Toronto Police made almost 3,300 calls to border officials in eight months — and 83.4 per cent were "status checks," says a new study.
Of the Law Societies of Upper Canada and Nunavut