I think the switch off experienced *are* the safety systems cutting in. The EMI will cause deviations in the electronics (be they a blocked CAN, corrupted sensor input or miscalculations in the MCUs) which the safety mechanisms will react to by switching apparently malfunctioning systems off. This would explain the dashboard warning lights.
Obviously relying on the safety systems to switch the car off is a dangerous approach. Those systems are designed to detect e.g. 99% of all errors in time. With a low electronic failure to start with, this leads to a reliable car as the very majority of the few errors happening is caught by the safety system and the remaing (we talk about e.g. 10^-8 per hour here) failures of one system might still be handable by the driver supported by the other electronic systems in the car.
This device - if used widely - inreases the basic error rate significantly and supresses all electronics. There might be a reason they tried it only with a car driving 24 km/h.