I've not heard that this has actually been needed to be implemented yet, but it makes a lot of sense to have mechanisms to remotely implement load balancing if people won't voluntarily do it themselves.
The National Grid has for many years (at least since 2008 or so, when I first saw it) had a well-defined process for managing situations of reduced electricity supply through rolling blackouts, initially for just half an hour at a time but with the capability to extend for longer if needed, but as far as I'm aware it's never had to be implemented. The Grid is constantly running on a fine balance between supply and demand, that's how the whole system is designed to operate, and EV chargers are just one more way to help balance that load - not only in terms of load (the chargers) but also in terms of supply (V2G). The latter is going to offer potentially some useful extra income for EV owners when wholesale electricity spikes come.
The thing to remember with all this kind of resilience and capacity planning is that it makes excellent engineering sense to design the capability into the systems right from the start, even if it's never going to be needed.
