>>1935715Montreal, you buy tickets for individual trips, in certain parameters. Like a ticket to travel through "Zones A, B, C, but not D." If you have a digital fare card, it just contains your tickets. Except, there's no good way to tell it which tickets to redeem, so you generally can only load them with one type of ticket for each service. Also, the tickets all have expiration dates, because god forbid you bought a ticket last time you visited Montreal that was 20 cents cheaper than a ticket today.
Ontario has many services using "Presto", which is a cash-based digital fare card. You put dollar amounts on the card, and each service just deducts the appropriate amount from the card balance based on its price. So the Toronto Transit Commission just deducts the cash fare for 2 hours of travel anywhere in Toronto. While something like the GO Train, with approximately distance-based pricing, you tap once when you get on and it reserves a fare for the theoretical maximum trip, and when you tap off it releases the hold and charges you based on your actual travel distance. Because it's cash based, there is no expiration (government laws here protect cash-balances like gift cards, etc...).
Cash-based systems are also theoretically interchangeable to other payment methods, like credit or debit cards. In Vancouver, you can tap a credit card the way you'd tap their digital fare card. But some systems like to minimize payment processor fees and restrict you to loading and using digital fare cards.
