CAllCrmLead::AddObserverIDs

static function AddObserverIDs($ID, array $userIDs)
{
	if(empty($userIDs))
	{
		return;
	}

	$observerIDs = array_unique(
		array_merge(
			Crm\Observer\ObserverManager::getEntityObserverIDs(CCrmOwnerType::Lead, $ID),
			$userIDs
		),
		SORT_NUMERIC
	);

	$fields = array('OBSERVER_IDS' => $observerIDs);
	$entity = new CCrmLead(false);
	$entity->Update($ID,$fields);
}