RE: Bounded Contexts, Domains (Core, Supporting, Generic), and data imports

BCs don't have to be physically separated, it could just be a logical separation. Although they could be deployed separately. But you are correct, there should be only one "owner" of the information within a BC and other BCs can use operations exposed by others to retrieve and manipulate the information stored.

In your specific case, you can develop the supporting contexts within the Training app as if they were separately deployed. Create a service layer around the HR Context that the Training App uses to interface with the yet to be developed HR App. In the future, the HR App could be separated and the Service layer could be exposed as a true service.

--Mike