Примерно так будет:
$Shop_Cart_Controller = Shop_Cart_Controller::instance();
$aShop_Cart = $Shop_Cart_Controller->getAll($oShop);
foreach ($aShop_Cart as $oShop_Cart)
{
$oShop_Item = $oShop_Cart->Shop_Item;
$oShop_Item->getPrices(); //массив с основной ценой
$aShop_Specialprices = $oShop_Item->Shop_Specialprices->findAll();
foreach ($aShop_Specialprices as $oShop_Specialprice)
{
$oShop_Specialprice // объект специальной цены
}
}