Starting with ProTools 8.0.5, Avid no longer supports new development for HUI protocol and has left HUI inside Pro Tools as a 'Legacy Protocol'. A clarification of what is supported in Pro Tools for HUI can be found in the Digidesign User Conference site here: http://duc.avid.com/showthread.php?t=338093.
We have tested FaderPort in HUI mode with many versions of Pro Tools to show the differences in behavior between releases.
*NOTE: The FaderPort itself has never changed its HUI mode implementation. Any differences or changes in functionality from version to version are a reflection of changes in Pro Tools HUI implementation and support.
Link to the above PT compatibility chart can be found here.