preserve_files = TRUE but files deleted on rollback

I want migrate files first and then use migrated files in node file/image fields. All files (AttachmentsMigration) are migrated and registered to drupal file_managed table without problem. But if i use rollback for my nodes (ArticlesMigration) my files are always deleted from disk and file_managed database.

I try use

$this->addFieldMapping('preserve_files')
         ->defaultValue(TRUE);

but without success. I try debug in file.inc and for some reason there is no entry in file_usage table.

Here is relevant part of migration class:

class AttachmentsMigration extends HNMigration {
  public function __construct($arguments) {
    parent::__construct($arguments);

    $this->description = t('Migration Attachments from mongodb to Drupal');
    $this->dependencies = array('PrepareAttachment', 'PrepareImage');

    // We instantiate the MigrateMap
    $this->map = new MigrateSQLMap(
      $this->machineName,
      array(
        'old_id' => array(
          'type' => 'int',
          'unsigned' => TRUE,
          'not null' => TRUE,
          'description' => 'ID z ceskeho API.',
        ),
      ),
      MigrateDestinationFile::getKeySchema()
    );

    $query = db_select('hn_migrate_attachments', 'ma')
             ->fields('ma')
             ->orderBy('old_id', 'ASC');

    $this->source = new MigrateSourceSQL($query);
    $this->destination = new MigrateDestinationFile('file');

    $this->addFieldMapping('value', 'data')
         ->callbacks(array($this, 'convertDataToURL')); // create url from MongoDB grid_fs ObjectId
    $this->addFieldMapping('destination_dir', 'old_id')
         ->callbacks(array($this, 'getSubDir'));  // create subdir
    $this->addFieldMapping('destination_file', 'filename')
         ->callbacks(array($this, 'cleanupFileName')); // transliterate filename
    $this->addFieldMapping('file_replace')
         ->defaultValue(MigrateFile::FILE_EXISTS_REUSE); // reuse files
    $this->addFieldMapping('preserve_files')
         ->defaultValue(TRUE); // preserve files
  }

  /**
   * Prepare entity before import begin.
   *
   * @param type $entity
   * @param type $row
   */
  public function prepare($entity, $row) {
    // nastavime povodne meno suboru
    $entity->filename = $row->filename;

    // is file image type?
    if ($image_info = @getimagesize($entity->value)) {
      $entity->type = 'image';
      $entity->filemime = $image_info['mime'];
    }
    else {
      // use file_entity file_get_type() function for determine type of file
      $entity->type = file_get_type($entity);
      $entity->filemime = $row->mime_type;
    }
  }
}

Thanks for advice.