I was looking for something unrelated to this on the Etihad website and came across the following which seems to be unambigous. I assume there must be some underlying legislation or court case which explains this. In fact with Etihad, the interpretation appears to be even wider than with Emirates given that it relates to any ticket purchased in Italy and not just a ticket departing ex-Italy.
What do I do if I missed / did not use the first flight part of my ticket which was purchased in Italy?
If you have purchased your ticket in Italy, (either from our tickets office, call center, an authorized travel agent or through our website
Etihad Airways Global - National Airline of United Arab Emirates) and you have, for any reason missed or didn’t use, the first flight of itinerary, but would still intend to take the subsequent flight (in case the departure of the latter is provided over 12 hours after the arrival of the flight not used) or the return flight initially booked with the same tariff, without any additional payment or fare adjustment, you must contact us within 24 hours following the departure of the unused flight by calling +39 02 23331300 requesting us to hold the validity of remaining flight reservations. If the departure time of the next flight is within the 24 hours from the first flight, you should contact us at least 2 hours before the departure time of the next flight. If you inform your intention in the above manner, we will reissue your Ticket for the remaining itinerary without any additional payment or fare adjustment. If you fail to do so all remaining flight reservations will be canceled and in the event you decide subsequently to travel using such ticket, we will, subject to availability of seats, charge you for the difference between the original ticket purchased and the highest fare in the same class of travel applicable to the modified itinerary at the time of ticket reissuance. In the event the fare rules of the original ticket are more favorable to you, those will be applied.