According to the documentation here:
http://code.google.com/googleapps/domain/audit_admin/v1/using_api.html#GA_admin_audit_params, you should be able to query audit activities for a specific event type (CALENDAR_SETTINGS, CHAT_SETTINGS, etc), but my experience has been that "eventType" query parameter is ignored. (I've had no problems with other query parameters like maxResults, eventName, continuationToken...)
Is this a known issue? If so, is there a fix on the way? If not, is there some sort of black magic involved in filtering by a specific event type? Any information on this would be appreciated.