If there is an existing metastore for the region, doesn't mean my organization store all the meta data across the workspaces in a specific metastore or data lake ? 

Databricks suggests to have one metastore per region. How the project specific metadata and access can be managed ? Moreover storing the project specific meta data in our own data lake and storing the project data in our own external lake would make more sense. 

Having a metastore for all the workspaces (Dev, UAT, Prod) and external data lakes separately per environment is being followed across industry ?