If I recall correctly, the internal drive bays in the FAS2000-series shelves use a special SAS plus power SCA-style connector, while the external SATA drive shelves use a FC midplane (the SATA drives that are used in such shelves include a SATA to FC converter board as part of the drive tray assembly).
Therefore, you would not be able to use a SATA drive from an external shelf in the integrated drive bays.