It happens when a person's file is sent to the review board. When the criminal court has finished the trial, with a verdict of not criminally responsible or unfit to stand trial, the individual's file is sent to the review board. At that point, the board takes over the individual's file and checks whether a victim wants to be made aware of the hearings that will take place in subsequent years. They keep a registry.
Each board has its own procedures, but, as a general rule, it gathers that information and sets up a registry when it takes on a new file. I also believe that victims' support services, which can be found across Canada, provide their assistance in those situations.