"the typical sound of a line ready" -> dial tone?
What would you normally hear when you picked up the receiver on a payphone, before you inserted coins? In my US experience in the 90s, if I were using a payphone, I'd pick up, listen for dial tone, insert my coins, (hear the coi tones, dial tone would pause and come back, IIRC), then dial the number, etc. If I just dialed a number without insering coins, I'd get a recorded announcement that I needed to insert coins; unless it was a free call. From movies, I gather older pay phones didn't let you make free calls generally, you'd need to insert coins before the dial tone; maybe that was common where you lived too?
As I understand it, the payphone phone lines I interacted were specially configured and had additional signalling so the phone company could determine free or paid at the central office and the payphone would signal payment. Private payphones existed where the phone line was normal and calling rates were determined by the phone itself, but it's trickier to do that right.
It makes some sense that a private payphone that would let you make free calls to the 11X numbers might have a synchronization issue. Dialing 111 wouldn't ever connect anywhere in Italy (I think?), but might have triggered the call is paid behavior, and hanging up quickly may have cancelled actually dialing without the phone realizing. There's a lot of tricky timing with detecting hang ups, and exploiting differences in timing gets you into being a phreaker.
As for who paid, if these were private payphones, probably the owner of the phones. Otherwise, the phone company.
You might enjoy this series of audio recordings: http://www.evan-doorbell.com/production/group1.htm