Bug #6371 is a duplicate of this one, but has a potential patch.

Jan, I believe you did the relevant work here.

From Calendar

Select Manage calendars from right expando-manu

Select change permissions icon on right of an existing calender



In Permission window

Enter Bob in individual users input area and select all options except 
delegate

Push Save Calender Submit  button

No w enter John in individual users input area and select all options 
except delegate

Push Save Calendar Submit botton

it will return Individual user list

Bob

bob@hurleybulldogs.com

John



Enter Jim in individuall users input area and select all options 
except delegate

Push Save Calendar Submit botton



it will return individual user list

Bob

Bob@hurleybulldogs.com@hurleybulldogs.com

John

John@hurleybulldogs.com

Jim



Now de-select all permission options under individual Users - deleting them

Push Save Calendar Submit botton

it will return the list

Bob

John

Jim







--------------------------

Here are the hooks



  if (!function_exists('_username_hook_tobackend')) {

      function _username_hook_tobackend($userID)

      {

          $vdomain = '@hurleybulldogs.com';

          if (substr($userID, -strlen($vdomain)) == $vdomain) {

              $userID = substr($userID, 0, -strlen($vdomain));

          }



          return String::lower($userID);

      }

  }



  if (!function_exists('_username_hook_frombackend')) {

      function _username_hook_frombackend($userID)

      {



            $vdomain = 'hurleybulldogs.com';



          return String::lower($userID) . '@' . $vdomain;

      }

  }