Is it possible to use ['#attached'] to load libraries form library API?

Not sure if this is what you meant exactly but this is an example that works:
http://api.drupal.org/api/drupal/includes!ajax.inc/group/ajax/7#comment-...

Yes it's possible:

$form['myelement']['#attached']['libraries_load'][] = array('myAwesomeLibrary');

So, in short, just add a libraries_load key to your #attached array, with as value an array of parameters to pass to libraries_load().

Note that this:

$form['myelement']['#attached']['libraries_load'][] = array('myAwesomeLibrary');

Should be this:

$form['myelement']['#attached']['libraries_load'][] = 'myAwesomeLibrary';

@Jaypan:

No it should not ;-)

See drupal_process_attached():

// Add additional types of attachments specified in the render() structure.
// Libraries, JavaScript and CSS have been added already, as they require
// special handling.
foreach ($elements ['#attached'] as $callback => $options) {
  if (function_exists($callback)) {
    foreach ($elements ['#attached'][$callback] as $args) {
      call_user_func_array($callback, $args);
    }
  }
}

The second argument to call_user_func_array() should be an array :-).

Oh, you're right. I had an additional array layered in my code I was working on.