At present, the page_title module doesn't pre-populate the page title on a node which is being created as a translation from a source node which has a page title entered.

For example assume we have node/55, which is in English, and has a page title entered. If the (core) translation module is turned on, you get a "Translate" tab on node/55/edit. Click that and you can create a translation of node/55 into any other enabled language. If you do this for say German, you will get a node creation form which is pre-populated with the form field values of the original source translation (English). In other words, node 55's title, body, CCK fields etc are all carried over. However the page title is not.

This can be fixed by modifying the IF code at line 132 as follows:

<?php
    if (variable_get($key, 0)) {
      // If there's no page title in the node, check if there's a page title in the source node if this is a translation.
      $default_value = !empty($form['#node']->page_title) ? $form['#node']->page_title : $form['#node']->translation_source->page_title;
      $form['page_title'] = array(
        '#type' => 'textfield',
        '#title' => t('Page title'),
        '#description' => t('Provide a description of this node to appear in the &lt;title&gt; tag which search engines can use in search result listings (optional). It is generally accepted this field should be less than 70 characters.'),
        '#default_value' => $default_value,
        '#size' => 60,
        '#maxlength' => 255,
        '#weight' => -4,
      );
    }

The guts of the change is:

<?php
      $default_value = !empty($form['#node']->page_title) ? $form['#node']->page_title : $form['#node']->translation_source->page_title;

which is essentially just saying, if the node doesn't have a page_title then check if there is a page title on a node->translation_source.

Let me know if you'd like a patch for this change.