When you enter the autostrada you pick up a ticket, you give it back at the toll booth exiting.
Actually, there are no toll passes at all, each trip is separately charged. The closest thing would be a telepass, that is a radio transponder installed on a car; passing through dedicated toll lanes, the fee is directly charged on a bank account. It is very unlikely that a rental car comes equipped with a telepass, as this is convenient only to long term users.
As for speed cameras, north of Florence speed cameras are linked by an electronic system that may measure not only your top speed but also your average speed on a stretch, shooting photos when you enter and when you exit the stretch and checking the time. So being warned about speed cameras is basically useless, as you have to be sure you are not overspeeding all the time. This system is called "tutor" and it is said to be so efficient that police has at times to switch it off in order to not be overwhelmed by the administrative work of issuing fines.