In this part of the book, Doc and Mac are discussing how the strike is going. Mac says to Doc that the valley is organized like Italy. This means that the fruit growers have all the farms in the valley completely controlled.
This is a reference to how Italy's government was at the time. Benito Mussolini had set up a fascist government -- sort of like the Nazis, except not all that anti-Jewish. This government kept all aspects of life under its control. It is also said to have been efficient. There is a famous saying that at least they made the trains run on time.
So the allusion is to a place that is tightly controlled by the authorities -- Mac is saying that the growers control everything so it is hard to have a successful strike.
If you need to cite proof for this, follow the link, and search for "Mussolini" in the book.