Canada just launched their nationwide Emergency Alert System. It features a red bar and an automated voice that covers the program you are watching. In this clip it covers a news broadcast from CityNews. Citytv handles the alerts nicely, rather than allow the report to continue to play in the background. They immediately switch to an exterior view of their building in YongeDundas Square. I guess they were caught off guard for the first alert. The 2nd time the meterologist was ready to go when the second alert came through.
The on-air appearance of those alerts are not uniform as the provinces usually have a larger say in these matters. The example you have shown is not what they do in my province.
This link explains it and has links to the individual provinces and territories.
Neither the voice-over not the red banner are particularly clear, are they? I appreciate they have to be generated on the fly, but if you only notice the interruption after a few seconds, you've missed all the important details.