tzdata2005r was released on 27 Dec 2005. This 2005r release includes DST rule changes for Canada as follows.

# CBC News reported that Ontario and Manitoba have announced plans to
# follow the US change, and that Nova Scotia is considering it; see
# <http://www.cbc.ca/news/background/daylightsavingtime/> (2005-10-21).
# CBC news also reported that Prince Edward Island is the first
# province in Atlantic Canada to follow the US change, and that Quebec
# had agreed; see <http://www.cbc.ca/pei/story/pe_daylight_20051207.html>
# (2005-12-07).
#
# To reflect all this, the Canada and Winn rules have been adjusted to
# agree with the 2007 US change.  This means we assume most of Canada
# will fall into line.  However, Alberta, British Columbia,
# Newfoundland, Northwest Territories, and Yukon already have separate
# rules in our database, so for now we'll leave them alone, which
# means that we currently assume these regions will not change their
# rules and will disagree with the US starting in 2007.  This
# assumption is probably incorrect, with the possible exception of
# Newfoundland.  We plan to adjust the Edm, Vanc, StJohns, and NT_YK
# rules as the corresponding provinces make their announcements.