He has also been a representative of the Regroupement des commerçants de la rue Ontario, working on local issues involving crime, prostitution, and development.
He was the sole councillor to vote against a local $15 million surtax for new recreational and cultural services in 2006, arguing that the funds should have come from the entire city.
[4] In September 2007, Ville-Marie borough mayor Benoît Labonté and councillor Karim Boulos resigned from Tremblay's party to sit as independents.
[5] Labonté and Boulos eventually joined Vision Montreal and formed an official governing caucus in conjunction with Mainville.
In late 2009, he introduced a successful motion demanding that city council ask the provincial government to hold an inquiry into allegations of corruption in Montreal's construction sector.