There is a challenge to integrate lightning components from different managed packages. There raised a question "Are the communication between the components from different namespace is possible ? "
As per my understanding, I confirmed yes; but others are not satisfied on that. So we have raised a case for Salesforce support and described our problem to them. They confirmed that inter namespace communication is not possible in locker service.
Since I have still doubted on that, I done a POC with different namespaces.
In the 3rd org, I can success fully run the application by passing attribute values from parent component (namespace1) to child component (namespace2) also using the events I passed the data back from child to parent componet.
So I can confirm, the communication between lightning components which are in different namespace is possible, rather than the Salesforce support.
Its my experience !!!