It is possible.
When a predefined object (a GameObject prefab) is dynamically instantiated, if it has a StrixReplicator attached to it beforehand, the object is automatically replicated, and its replicas are created on other clients. At the same time, the values of the object’s properties that are subject to synchronization are also synchronized. Ordinary object initialization events (such as the Start callback in Unity) are executed when a replica is created, so any processing triggered by the automatic creation of the object is possible using these events.
On the other hand, if you require that notifications of dynamically created non-replicated objects (i.e., GameObjects that have no StrixReplicator attached) be made, STRIX itself has no such feature, unfortunately. Instead, clients can implement this feature by sending a custom message from the client that created the dynamic object to other clients using RPCs or message relay features.