Exactly, the entity framework model completely replaces the need for the DataObjectBase. If the class would be rewritten at this time, its name would have been "ModelBase" (in the MVVM naming conventions).
You have 3 options:
1) Make your model public => bind directly to the model (but then you have no freedom in the validation, etc)
2) Use the ViewModelToModel attribute => if you want to use the properties inside your view model
3) Use the Expose attribute => if you want to protect your model, but don't need to access the properties in your view model