i used to work for BN, on the suburban trains. Unlike most of the other lines, except the UP (C&NW), they are BNSF employees, not Metra. Some of my facts may not pertain to Metra employees.
The agent at Aurora supplied the ticket books. The tickets were called duplexes. As stated, one for the passenger, and one for the company. The agent would record the number series of the tickets, and to whom they were issued. Every trainman and conductor has a punch with a unique mark. Mine was an upper case E. The train crews supply their own change money. It was wise to only have enough tickets for immediate use. Loss would require paying maximum fare on all outstanding tickets. Guys would turn them in if bidding freight for an extended time. The Metra agents at CUS could supply tickets too, it i was running short. Their tickets were from a whole different number series.
The tickets and proceeds needed to be remitted within 5 days, or the company might invite the employee to an investigation. This was sometimes tricky for extra board guys. They might get stuck out of town, and remit on the 11th. hour. The company had auditors who would add up the tickets and make sure that the proper sum was received. Sometimes they would issue a correction letter. This was if the remitted sum was off. I worked a job in the evening. All of the agencies were closed except for Aurora and CUS. This meant cutting hundreds of cash fares. Sometimes I would make a simple addition error. I would then have to cough up the dollar or two that I missed in my calculation.
The trains had spotters on them sometimes. These were like mystery shoppers. They would make sure that the train crew was professional. They would also look for the crews not charging. Between the spotters and the unique punch marks, management had a fairly tight control on its funds.