Hi, Giangilberto from Milan, so what you posted is the only official Italian source regarding strikes because it comes from the Ministry of Transport, so if the proclamation no longer appears in the MIT register, it most likely means that it has been revoked.
I just checked the website, and there's no strike listed for September 26th.
A small clarification: "revoked" and "no longer scheduled" are not formally the same thing, and for a ferry, that matters. The register collects the announcements, and operational confirmation is provided by the company, which communicates which trips it operates.
There are several companies that cover the same route, Caremar, SNAV, and Alilauro, and in the event of a strike, each communicates separately which trips are guaranteed. Therefore, the source to look at isn't generic: it's the operator with whom you hold the ticket.
Law 146/90, which regulates strikes in Italy and therefore also the guaranteed essential services, states this:
Article 1, paragraph 2, letter b, includes among essential services "urban and extra-urban public transport, including road, rail and tramway transport, air, airport, and maritime transport, limited to connections with the islands."
So the connection with the islands is expressly an essential service.
And Article 3 states the consequences: companies are required to guarantee, in agreement with the unions, the services essential for the movement of people and the supply of goods—notifying users accordingly.
The law requires each provider to disclose the services guaranteed.
The advice is, if the strike is re-proclaimed or if it reappears on the ministry's website, to check the company you purchased your ticket with, not a generic source.