Yes, the object manager is available in all Aurelius events, in the property Args.Manager. However, you must explicitly cast it to a TObjectManager.
Aurelius args cannot be available in XData events, because they are very different, even though look similar. Aurelius events are lower level and are called for every entity ("table"), being updated, and in the middle of the Aurelius mechanism for updating the table. XData events are higher level, they are called only once, when the CRUD endpoint is invoked.