What kind of lines?
I wonder if you can get your service provider to not display CLIP info to the called party when they recieve the DDI number of the extension if its ISDN or SIP? POT's lines I doubt it is possible. I have never found a privacy option that deals with this on a 3300. There was one on the 3100 where you could have all calls private (no cli from the system) but use a key to release it if you wanted...or it could have been the other way round