http://www.ercot.com/news/releases/show/225151
That links to this PDF which describes their emergency procedures:
http://www.ercot.com/content/wcm/lists/200198/EEA_OnePager_u...
Basically, there are 3 levels of response:
(1) Reserves below 2,300 MW: get more power, including from other grids.
(2) Reserves below 1,750 MW: interrupt power to industrial customers (who've contractually agreed).
(3) Reserves below 1,375 MW: order transmission companies to reduce demand (i.e. rolling blackouts).
The reserves are shown on their main page (http://www.ercot.com/), and when I've checked today, it has been roughly 3,500-4000 MW. So that sort of sounds promising, but the graphs on the same page (projected capacity and demand) don't look as promising.