As was recently reported on Linux.com, the Green Party of Canada became the first party to officially endorse the use of open source software in their party platform. The move was largely influenced by a member of the relatively new Free Geek Vancouver, and hopefully will influence other parties to follow suit in the future. The New Democratic Party has had some mentions of open source on the provincial level and by individual members in the past, so they are probably the most likely to do so soon.
To point out this position and encourage the other parties to add a similar one, use the following contact information:
NDP: Online Form
Liberal: Provincial/Territorial Association list
Conservative: Online Form