In many places with POP, it is (former) conductors with additional education who are the roving inspectors. If you get caught without ticket, the roving inspectors will sell you a regular full fare ticket for your intended trip, and take the fees (it is not a fine) in cash (although with modern communication systems, credit card transactions would be possible as well). If you don't have enough cash available, your identification is taken, and you get an invoice to be paid within a few days. Only if you don't do that, it gets to court. Now, if you simply forgot your (monthly) pass, you still have to pay, but you will be reimbursed (minus some handling fee), and that's it. Simple, non-bureaucratic, and it does work.

About consolidated fare systems: The successful models have a general organization which has the responsibilty over services; the German name is "Tarifverbund". This organization has the contracts with the operators, and in many places, these contracts are regularly put up for bids. All the revenue from tickets, passes etc. goes to the Tarifverbund which then distributes it to the operators, according to their share of the passengers. Regular passenger counts are used to determine these shares, and they are quite reliable and accepted by the operators. Now, if the cooperation goes beyond fares, we have a "Verkehrsverbund", which also has the responsibility for schedules. Most Tarifverbund and Verkehrsverbund models are a big success (sometimes even become a victim of their success…).