True - but the law does mention an "annual" tax, and the actual implementation has to be defined by the "Dirrettore dell'Agenzia delle entrate" so it is quite possible there will be a provision for partial payments such as there is for boats. I mean what if you buy your (Italian-based) airplane in December, you're certainly not going to pay for the whole year?
That would require too much of a reasonable attitude, IMHO. Wrong country for that.
If you buy a plane and register it in Italy, then there is a provision in the law for a prorated payment for the first year of ownership. As I said previously, the whole "this applies to foreign registered planes" thing was added on rather hastily and definitely not well thought out. My personal opinion of what will happen is: absolutely nothing. As nobody is currently tasked with actually levying the tax for foreign registered planes, nobody will and that'll be that.
So, in the end not a cent will likely be paid but some people will be scared off (possibly permanently) from flying to Italy on holiday and this will certainly benefit neither the local nor the national economy.
Ciao,
Dg800