I have some of the CP600 phones. We are upgrading to OSV in the near future, but I like to play with the shiny new toys, so I flashed them to HFA. If you have a DLS server, you can update the firmware there or with the phone's web interface. They will barely work on my V5 4000. You can make and receive calls, and that's about it. I ended up flashing them back to SIP so I can at least have "some" functionality.
LoPath
Maintain HiPath 4000 V5 & V6, OpenScape Xpert V4, OpenScape Xpressions, OpenScape Contact Center, OpenScape Voice