I lived in Antwerp for six months in 1972 and was impressed with public transportation that was good enough for that time but there was not an underway system yet. Eleven years later I visited Milan for three months and found there was a very interesting public transportation system where tickets had a fix time limit after the initial trip. Time duration was 75 minutes and you could take any trip in any system while ticket was alive, with the exception of metro where just one trip was allowed. The ticket was marked just one time in the very initial trip (also at the metro) and in case time duration was completed while in transit, you were obliged to mark a new ticket. Bus or tram drivers didn't care about this problem and they were not allowed to sell tickets. You had to by them at the metro stations or newspaper stands. This obligation was checked by inspectors visits to the buses and they were very strict with cheaters, keeping their Id card and giving a date ticket for a trial or the payment of ten times the amount of the ticket.
Being both systems so similar, would like to know if there is certain relation with the italian organization.