Did they ("Europe Advice") really read and understand that law before writing their letter? The tax also applies to Italian residents, therefore this point will certainly not help.
Yes, they did:
Article 14 bis of
the decreto-legge seems to impose the tax on foreign registered aircraft
that remain in Italy for more than 48 hours with the possible consequence
that a foreigner visiting or conducting business in Italy in an aircraft or
2 days must pay the same amount as does the Italian resident for an entire
year. This could mean for you that you have to pay a lump sum of 450 per
year if you fly to Italy with your glider or balloon and stay there for
longer than 48 hours.
Once applicable, Article 14 bis of the decreto-legge could therefore indeed
pose a problem under European law: