If your question is more about actual RDBMS level usage such as whether users are logging and and actively working with a specific VDB, then the answer is no.
Since the Delphix Engine is a storage appliance, as Srish says, we store and can display a lot of information about storage utilisation in the Dashboard (and also in the Capacity Management screen). However, to find out how often users are logging into a particular VDB you need to use whatever admin tools you normally would for that RDBMS (be it MSSQL, Oracle, ASE admin tools, queries, and commands).