set accessibl for OG member or Buddies (buddylist)

Yes, possible... I will be adding some more fine-grained permissions for Private Number after moving my site to a new server. I will look into adding OG or buddylist support then.

Thanks for the suggestion.

There are too many buddy-type modules to support. So what I did was add hook_private_number_access() which you can either implement in your own custom module or add a feature request on the contributed module to support the hook.

http://drupal.org/node/425596