Eager loading relations in Plugins Element Type
Ok, so i managed to solve my problem without actually fetching any extra records, but instead using mysql group_concat function for the fields i need to display. Posting this here for anyone else that might need it.

In OrderElementType:

public function modifyElementsQuery(DbCommand $query, ElementCriteriaModel $criteria){

    $query
      -&gt;addSelect('group_concat(items.productName separator \';\') as productnames')
      -&gt;join('orders orders', 'orders.id = elements.id')
      -&gt;leftJoin('items items', 'orders.id = items.orderId'
      -&gt;group('elements.id');
}

public function populateElementModel($row){
  $model = OrderModel::populateModel($row);
  $products = explode(';', $row['productnames']);
  foreach($products as $product){
    $item = new ItemModel();
    $item-&gt;productName = $product;
    if(!$model-&gt;items){
      $model-&gt;setAttribute('items', array());
    }
    $model-&gt;setAttribute('items', array_merge($model-&gt;items, array($item)));

  }
  return $model;
}