I do not know much about Oracle Mobile Server with Oracle Lite, does it use SQLite or BDB? I do know that databases created by SQLite cannot be read by Berkeley DB SQL (of which dbsql.exe is part of), and databases created by Berkeley DB SQL cannot be read by SQLite. Also, databases created by Berkeley DB outside of the SQL API cannot be read by the BDB SQL API. You can open BDB SQL databases with BDB outside of the SQL API, but I would not recommend that outside of a few BDB utilities described in the documentation. So if your BerkeleyTest database was created by SQLite or BDB outside of the SQL API, then it makes sense that dbsql.exe is returning an error when trying to read it.
Calling dbsql.exe BerkeleyTest does not open the database, that happens when the first operation is performed on it, which is why you did not get an error until you tried to select something.