If the transformers are the points of failure, it would seem that some engineering would be in order, so as to tolerate events like this by cutting out until the electromagnetic environment becomes safe again. At least the flares are not threatening to do what a man made EMP would.
Apparently the plasma travels far slower than light, so we’d have many hours of warning. Shutting down the grid for a number of hours, even days, would be very inconvenient (and a bit expensive - think about lost food, etc.), but you’d be able to start it up again and fix the damage. But we’d still need spare parts, a coherent plan and spare food and water available.
EMP would be a real killer - no warning, and a far more harmful pulse of energy. Much of the planning would protect against both events, and not be too expensive (at least not compared to bailing out corrupt investment bankers).