Hello Sophia123
No, it is valid as far as Milano Centrale, Milano Porta Garibaldi, or Milano Cardona, yet not for Milano city public transport.
With cross-border tickets and travel cards, you can use all modes of transport in Ticino and Lombardy that are part of the Arcobaleno fare network, as well as Trenord regional and suburban trains. See the Validity plan of cross border tickets on this page: Tickets | TILO ā Cross-border tickets ā Validity plan of cross border tickets.
Kindly note: the Arcobaleno day passes are only valid on TILO (RE trains), yet not on EC trains!
Best regards,
Roland