Craft Form Event - Target a Single Form
The following code fires the onBeforeEmailSubmission event (link)

// Fire an 'onBeforeEmailSubmission' event
$event = new Event($this, array(
    'email'      =&gt; $notificationEmail,
    'submission' =&gt; $submission,
));
$this-&gt;onBeforeEmailSubmission($event);


So you'll have access to the $submission and to the $email as array keys in your $params variable. In order to get the form you have to do 

$submission = $params['submission'];
$form = $submission-&gt;getForm();
if($form-&gt;handle === 'whatever'){
     // do something
}