idea behind this would be:

BIM360 is the collaboration platform, on this platform the current version of a Revit-model will be worked out. But this is not a platform for document management. Once the project is terminated to model will be given back to meridian. If it changes again it will be reloaded to BIM360.

Meridian is the document-management system, it will keep track of all the main changes and the handover after terminating a project.