HPBX allows users to pick up other extensions calls if they are in the same pickup group. To setup a pickup group login to HPBX and go to features and then pick up groups
Click on the new button to create a new pick up group.
Enter in a name for the pickup group and select the telephone extensions that you want to be in the group. After you have selected the extensions press save. Now when a call goes to another extension dial ** on your phone and it will pick up their call.