To be honest, the Liberals don't want election reform, at least not the way you think.

If we have proportional representation, the Liberals (and the Conservatives, let's be honest) would never govern again.

As it stands, it's quite possible to form a majority government with ~35% of the vote, which suits the LPC and CPC just fine, as they can just swap chairs every four to eight years. Under PR, they'd need to win >50%, which hasn't happened in almost fifty years, and even before that was still very, very rare. The LPC or CPC would need to share power with the NDP or BQ to get anything done, which means that a) parliament would have to represent the electorate, and the electorate is much for left-of-centre than the people they vote for, and b) the LPC and CPC couldn't depend on the favour of their donors since buying them wouldn't really worth the money it is today.

The Liberals would sooner go through a twelve-year term in the wilderness than see a Canada that's run like a western European country. So yes, they'd rather lose, and lose hard, knowing they'd be back in eventually, then advance real electoral reform and lose their sole access to the levers of power forever.