Vincenzo,
I am not sure I understand the issue you are attempting to solve. Users are mobile, but the DN's that they use are specific to them. In the CUP environment, a user would log into the CUP client with their userid/pw and that would make the CUP interface specific to them. Same thing as extension mobility.
Can you please explain more about the customer environment to help me understand the issue. Please explain the desktop move and the different IP phone and voip line statement you made.
Thanks,
Dan Keller
Technical Marketing Engineer