To clarify, it's not an app. It's a cell broadcast system.
For weather events right now, Environment Canada issues alerts for tornadoes and severe thunderstorms. For other weather events—and I had this conversation with other colleagues of yours in British Columbia—such as flooding, even though flooding is caused by a weather event, the alerts are primarily for anticipated damage, road closures and evacuation orders. Those would come from the provincial EMO. I understand the situation in B.C. now is that it has asked the regional municipalities to request the alerts.