For event definitions to be merged, the files provided to customize the events must be named the same as the existing files containing the event classes to customize. Placing event classes with the same name in files with different names will result in errors occurring when loading the event definitions onto the database.
The customizing behavior for events is very simple; events cannot be removed as existing functionality might be using an event that other components then decide to remove. Such code would subsequently fail to compile. This being the case the only change that can be made to existing event definitions is that event types can be added to an event class by other components.