Common enough; but I wonder if this is a symptom of new generation not keeping up with attempts to reduce emissions. Less coal/gas power generation & less wood-fired heating combining with a cold snap.
But the intent of a grid notice like that is to encourage generators to turn on more supply I think - its only a grid emergency notice that indicates supply isn't meeting demand.
The other thing that'll happen is where areas have ripple control they'll turn off hot water & street lights & whatnot to reduce demand as well.