Yes, but they still have the undecided category on their poll. They just factor it out later--to not do that is inaccurate.
At the Federal level I've voted for both the L's and the C's, and at the provincial levle I've voted L, PC, and NDP in different elections. For example, I voted both for Bob Rae and also for Mike Harris. My vote switches based on which issues I think are the most important at a particular moment in time. Parties tend to be narrow minded in their solutions to problems, and so often if you want to switch strategies you have to switch parties.
If I perceive that fiscal issues are the most important I'm likely to vote to the right. If I think an overhaul of our social policy is more important I'd vote to the left.
Sometimes I give my vote to the party with the most capable leader, regardless of ideology. It's often better to have the "wrong" ideology implemented competently than to have the "right" one botched. Much of the time the issues confronting the government have nothing to do with ideology and it's a skilled hand that matters more than anything else.