[hrunt]

According to the article, as the owner of the duplex, you would not be subject to the vacancy tax ("It applies to buildings with three or more units, not to single-family homes or duplexes").

As for your other points, yes, the government is trying to incentivize that inventory back on to the market (by disincentivizing keeping it off). Yes, they are doing it in response to a situation they took part in creating. Is this more or less likely than tenant termination freedom to result in more housing being available? That sounds like every market de-regulation argument ever.