LoaderService based on LoadDataFixturesDoctrineCommand. Basically all logic from the command extracted to reusable service class.

LoaderService.php

<?php
namespace Devhelp\Bundle\DataFixturesBundle\Service;

use Doctrine\ORM\EntityManager;
use Doctrine\Common\DataFixtures\Purger\ORMPurger;
use Doctrine\Common\DataFixtures\Executor\ORMExecutor;
use Doctrine\Common\DataFixtures\Loader;

/**
 * @author Paweł Barański <pawel.baranski1@gmail.com>
 */
class LoaderService
{
    private $entityManager;
    private $dataFixturesLoader;
    
    public function __construct(EntityManager $entityManager, Loader $dataFixturesLoader)
    {
        $this->entityManager = $entityManager;
        $this->dataFixturesLoader = $dataFixturesLoader;
    }

    public function load($dirOrFile, $append = false, $purgeMode = ORMPurger::PURGE_MODE_DELETE)
    {
        if ($dirOrFile) {
            $paths = is_array($dirOrFile) ? $dirOrFile : array($dirOrFile);
        } else {
            $paths = array();
        }

        foreach ($paths as $path) {
            if (is_dir($path)) {
                $this->dataFixturesLoader->loadFromDirectory($path);
            }
        }
        
        $fixtures = $this->dataFixturesLoader->getFixtures();
        
        if (!$fixtures) {
            throw new \InvalidArgumentException(
                sprintf('Could not find any fixtures to load in: %s', "\n\n- ".implode("\n- ", $paths))
            );
        }

        $purger = new ORMPurger($this->entityManager);
        $purger->setPurgeMode($purgeMode);
        $executor = new ORMExecutor($this->entityManager, $purger);
        
        $executor->execute($fixtures, $append);
    }
}

services.yml

parameters:
    devhelp.data_fixtures.loader.class: Devhelp\Bundle\DataFixturesBundle\Service\LoaderService
    symfony.data_fixtures.loader.class: Symfony\Bridge\Doctrine\DataFixtures\ContainerAwareLoader
 
services:
    devhelp.data_fixtures.loader:
        class: %devhelp.data_fixtures.loader.class%
        arguments:
            - '@doctrine.orm.entity_manager'
            - '@symfony.data_fixtures.loader'
 
    symfony.data_fixtures.loader:
        public: false
        class: %symfony.data_fixtures.loader.class%
        arguments:
            - '@service_container'