Remember: if an MP does not play ball, then the leader can choose to not approve that MP from running under the party banner in the next election. There are many other disciplinary actions available to the party to use against freelancing MP's - such as kicking them out of caucus. Good behaviour is rewarded. Bad behaviour is politically fatal. All MP's are- to a certain extent - trained seals.
What may be an interesting discussion is if everything in Canada needs to be a three -line whip. In the UK, it is totally normal for government backbenchers to ask zingers of the cabinet- and not, "I ask my colleague to please explain their awesomeness again." - i note that that discussion belongs elsewhere.
I think it is significant that in this case, the NDP MP was an accidental victor (visitor?) who fluked in. When an electoral sweep happens (such as the Orange Crush in Quebec for the NDP) then good people loose their seats and bad ones win. Numerous NDP 'warm body' candidates fluked into parliament. ( Can someone tell me again about people voting for the member and not the party.).
The real fun bit will be to see how many NDP MP's charge over to the Bloc. How many of them are strongly committed to Canada, and even more strongly committed to Quebec? The NDP will loose more. What if Peggy Nash wins leadership? What if they do not have their Quebec guy to vote for when voting NDP (Jack, more than likely, passed himself off as a Quebecer when in Quebec- note the Canadiens hockey sweater etc.)