accessing block type in the theme_preprocess_node()
You can't get access to a block object from a node preprocess hook; the context simply isn't passed down the chain.

As you're using a view, though, you can get hold of the View object, and test the name/display id. The basic idea would be:

function theme_preprocess_node(&amp;$variables) {
  if (!empty($variables['view'])) {
    if ($variables['view']-&gt;name == 'some_view' &amp;&amp; $variables['view']-&gt; current_display == 'block_1') {
      $variables['theme_hook_suggestions'][] = 'node__productstream';
    }
  }
}