Seems a private outfit called NERC has been handling our grid for a few years, and they proposed the "experiment". Assertions are that we may be wasting big bucks on precision we don't really need.

Which raises the Q, "how precise is it now"? I found the following alarm limits at NERC;

" The Frequency Trigger Limits (FTLs) are defined as thresholds. An FTL-Low alarm is generated when interconnection frequency is lower than FTL-Low for 5-minutes or more. The FTL-Low is 59.950 Hz for Eastern Interconnection and 59.856 Hz for Western Interconnection. FAL, as referenced on this chart, refers to the Frequency Emergency Threshold, where, once reached, system reliability quickly deteriorates. The FAL-Low is 59.908 Hz for Eastern Interconnection and 59.80 Hz for Western Interconnection.

An FTL-High alarm is generated when interconnection frequency is higher than FTL-High for 5-minutes or more. The FTL-High is set at 60.050 Hz and 60.144 Hz for Eastern and Western Interconnection respectively. The FAL-High is set at 60.092 Hz and 60.20 Hz for Eastern and Western Interconnection."

OK... that's pretty precise.