In parks during extra magic hours, I've always seen at least one CS place open. In Epcot, Electric Umbrella has definitely been open during EMH in the past... I don't know about other places (Seasons food court in The Land, random CS in World Showcase, etc.), but I'd imagine at least one or two other places would be open as well. Maybe someone else has experience there? Some of the TS restaurants may offer late seatings that push into the EMH as well, but probably not for the full three hours (I've seen people seated after normal park closing time in TS restaurants in EMH nights).
I can't find any info direct from Disney, other than "select dining options..." so the official site isn't really much help here.