The Event Pokemon from the Event Database are now listed in Dex for each Pokemon with their own tab. Obviously if there isn't any event's listed for a Pokemon, there isn't any. The Pokemon listed in each event tab are the same ones that would be listed if you filter for a specific Pokemon in the event database.

Dex Link: http://www.pocketmonsters.net/dex
Event Pokemon DB Link: http://www.pocketmonsters.net/eventpokemon