Don't these fare inspectors have the ability to know when and where the card was tapped?
Here are the term and conditions from link:Its not a PRESTO card its a ticket.
Using GO Transit e-tickets
Printed copies of e-tickets will not be accepted as a valid fare. To use your e-ticket or pass, you will need to be able to access the confirmation e-mail using your mobile device and an internet connection (data or a Wi-Fi). You must activate your e-ticket before you board by clicking on the ticket(s) or pass links in your confirmation email from your mobile device. Allow five minutes for your ticket to activate. Once activated, single-ride tickets are valid for four hours, and passes are valid during service hours on the day of activation. Each e-ticket has unique ticket number and you must display this identifier on your mobile device to a GO Transit fare inspector on request.