You may subscribe to Broker::Activity::EventTypeChange event. This system event is published when an event definition is changed. The corresponding event for client group change is Broker::Activity::ClientGroupChange.
Broker::Activity::EventTypeChange is published for the following actions:
created
definition changed
destroyed
information changed
The distinction between definition changed and information changed is that the definition is the event type’s fields, while the information is the event type’s infoset
#Universal-Messaging-Broker#webMethods#Integration-Server-and-ESB#broker