What if Canada used the Proposed British Electoral System?

The UK, the birthplace of the parliamentary system used by Canada, is having a referendum on switching their electoral system from first past the post to alternative vote. With the UK becoming a three party system, the two-party oriented first past the post system clearly produces distorted results, so as part of the coalition government deal between the Conservatives and Liberal Democrats, a referendum on electoral reform is happening. Of course the real question is why is there a referendum? Why not just do it? No other bill in parliament requires a referendum, so it's clear that when a government does not want something to pass (the Tories in the UK are against electoral reform) they put it to a referendum.

So let's assume the UK adopts this system (current polling has the British public divided, apparently half of Brits are opposed to a more democratic system), then why not speculate that Canada could adopt it?

So using the latest 2nd choice information from EKOS (April 18th), I've extrapolated what parliament would look like based on the latest polls, if we held the election under Alternative Vote, where you could mark your candidates in order of preference, rather than simply putting an X.

EKOS seat projections are currently:
Conservative 146
Liberal 69
NDP 44
BQ 48
Independent 1
Green 0

Using this data, but assuming the use of an AV electoral system, we get
Conservative 132
Liberal 90
NDP 47
BQ 39
Green 0
Independent 0

Obviously a mixed member proportional system that included preferential voting would be vastly preferable, but even with the very modest change of allowing the ranking of candidates, we see the Conservatives and Bloc take big hits in support, as they lose a number of ridings to the NDP and Liberals.

With AV, there is no longer any need for strategic voting. If your first choice is the unelectable Marijuana Party, you can feel free to put them as your first choice, while putting one of the bigger parties as your second choice, allowing you to influence the outcome of the election, without throwing your vote away.