(This story has been posted on The Wall Street Journal Online's Dispatch blog.) Posted by Jacob Bunge NYSE Euronext officials declined to comment ahead of any decision by ConEd on a power shutoff in parts of New York City, but the New York Stock Exchange has a backup generator ready to go in the event electricity is lost. As of midday Saturday, exchanges were planning to open trade as per normal after the weekend. Representatives of Nasdaq OMX Group Inc. and the New York Mercantile Exchange did not respond to requests for comment. The International Securities Exchange, which runs one of the biggest U.S. stock-options markets out of offices down the street from the NYSE, is prepared to staff its disaster recovery site in New Jersey, where its electronic systems are housed, according to a spokeswoman. -For continuously updated news from The Wall Street Journal, see WSJ.com at http://wsj.com.