http://www.theglobeandmail.com/news/british-columbia/bc-prof...
The Mayor of Vancouver is also interested in taxing non-occupancy and in the same special session of the legislative assembly that passed the 15% foreign buyer tax the Province granted the City of Vancouver (but not others) the powers to tax non-occupancy. It can be pretty involved to find out occupancy and the City has limited means so it'll be interesting to see if that goes anywhere.
The cynical answer to this by the way is that there's a Provincial election in early 2017, so in the near term appearing to address the problem is more important than addressing the problem in an effective way.
That would be much more difficult to enforce. You'd have to hire people to walk around knocking on doors or have neighbours snitching on each other. No thanks.
Simply require proof of residency in the property (or an active lease agreement / market listing) to qualify for a tax break. Otherwise, if you're parking-and-holding-without-using, you get slapped with a higher tax rate.