Все-таки нашла в документации:
$gr_res = CIBlock::GetGroupPermissions($IBLOCK_ID);
$res = Array(1);
foreach($gr_res as $group_id=>$perm)
if($perm<>"D
")
$res[] = $group_id;
$res = CUser::GetList($by="NAME", $order="ASC", Array("GROUP_MULTI"=>$res));
$gr_res = CIBlock::GetGroupPermissions($IBLOCK_ID);
$res = Array(1);
foreach($gr_res as $group_id=>$perm)
if($perm<>"D
")
$res[] = $group_id;
$res = CUser::GetList($by="NAME", $order="ASC", Array("GROUP_MULTI"=>$res));