RestrictionManager::getSitesByServiceId

static function getSitesByServiceId($id)
{
	if($id <= 0)
		return array();

	$result = array();

	foreach(static::getRestrictionsList($id) as $fields)
	{
		if($fields['CLASS_NAME'] == 'BitrixSaleDeliveryRestrictionsBySite')
		{
			if(!empty($fields["PARAMS"]["SITE_ID"]))
			{
				if(is_array($fields["PARAMS"]["SITE_ID"]))
					$result = $fields["PARAMS"]["SITE_ID"];
				else
					$result = array($fields["PARAMS"]["SITE_ID"]);
			}

			break;
		}
	}

	return $result;
}