Just got this update on the story from the BBC:

BBC News - Italy plans to tax Vatican on commercial properties

Looks like the Vatican WILL in fact lose it's tax-exempt status according to this report.

Excerpt
Prime Minister Mario Monti has announced the Vatican must pay taxes on non-religious property, from which it previously enjoyed an exemption.

The annual cost could be up to 720m euros ($945m; £598m) according to municipal government bodies.

Italy's Catholic Church has 110,000 properties, worth about 9bn euros.

It includes shopping centres and a range of residential property.