CAllCrmActivity::AttachBinding

static function AttachBinding($srcOwnerTypeID, $srcOwnerID, $targOwnerTypeID, $targOwnerID)
{
	$dbResult = \Bitrix\Main\Application::getConnection()->query(
		"SELECT a.ID, a.RESPONSIBLE_ID
			FROM b_crm_act a INNER JOIN b_crm_act_bind b ON a.ID = b.ACTIVITY_ID
			WHERE b.OWNER_TYPE_ID = {$srcOwnerTypeID} AND b.OWNER_ID = {$srcOwnerID}"
	);

	$itemFields = array();
	while($fields = $dbResult->fetch())
	{
		$itemFields[] = $fields;
	}

	$processed = 0;
	$responsibleMap = array();
	foreach($itemFields as $fields)
	{
		$itemID = (int)$fields['ID'];
		if($itemID <= 0)
		{
			continue;
		}

		$isBound = false;
		$bindings = self::GetBindings($itemID);
		$oldBindings = $bindings;
		foreach($bindings as $binding)
		{
			if($binding['OWNER_TYPE_ID'] == $targOwnerTypeID && $binding['OWNER_ID'] == $targOwnerID)
			{
				$isBound = true;
				break;
			}
		}

		if($isBound)
		{
			continue;
		}

		$bindings[] = array('OWNER_TYPE_ID' => $targOwnerTypeID, 'OWNER_ID' => $targOwnerID);
		self::SaveBindings($itemID, $bindings, false, false, false);
		$processed++;

		$responsibleID = isset($fields['RESPONSIBLE_ID']) ? (int)$fields['RESPONSIBLE_ID'] : 0;
		if($responsibleID > 0)
		{
			$responsibleMap[$responsibleID] = true;
		}

		\Bitrix\Crm\Counter\Monitor::getInstance()->onChangeActivityBindings(
			$itemID,
			$oldBindings,
			$bindings
		);
	}

	if($processed === 0)
	{
		return;
	}

	$responsibleIDs = array_keys($responsibleMap);
	\Bitrix\Crm\Activity\UncompletedActivity::synchronizeForBindingsAndResponsibles(
		[
			['OWNER_TYPE_ID' => $targOwnerTypeID, 'OWNER_ID' => $targOwnerID]
		],
		array_merge($responsibleIDs, [0])
	);

	if(!empty($responsibleIDs))
	{
		foreach($responsibleIDs as $responsibleID)
		{
			self::SynchronizeUserActivity($targOwnerTypeID, $targOwnerID, $responsibleID);
		}
	}
	self::SynchronizeUserActivity($targOwnerTypeID, $targOwnerID, 0);
	\Bitrix\Crm\Activity\CommunicationStatistics::rebuild($targOwnerTypeID, array($targOwnerID));
}