YC & CS Chew have explained the "Barnea fiasco". Many growers
(including our daughter) were caught and have mature trees that have not
produced a single fruit and won't until the pollinators get going.

Single varieties seem an excellent idea in Aus and NZ because of
the huge range of varieties being grown. In Italy oils are similar to the
great French wines where a mix of varieties has been established over a
long period to produce a wine that is characteristic of the varieties, the
climate and the soil. In Aus and NZ the varieties come from all over the
world and separate varietial or simple blends (Cab/Shiraz style) seems to
me to be a good way to start.

DOC regulations are different for each DOC area. I would suggest
contacting the Regional Minister of Agriculture for the main olive growing
regions of Italy. Write to the Giunta Regionale in Firenze, Perugia,
Bologna etc.
Cheers Brian Chatterton.