Enabling HTML in MENU_LOCAL_TASK titles (primary tabs)
The key is this if construct: if (!empty($variables['element']['#active'])) with regard to getting the titles of the inactive tabs to respond. My solution was to customize: theme_menu_local_task. Perhaps there is a better solution?

/**
 * Alter theme_menu_local_task.
 */
function my_theme_menu_local_task($variables) {
  $link = $variables['element']['#link'];
  $link_text = $link['title'];

  if (!empty($variables['element']['#active'])) {
    // Add text to indicate active tab for non-visual users.
    $active = '&lt;span class="element-invisible"&gt;' . t('(active tab)') . '&lt;/span&gt;';

    // If the link does not contain HTML already, check_plain() it now.
    // After we set 'html'=TRUE the link will not be sanitized by l().
    if (empty($link['localized_options']['html'])) {
      if (arg(0) != 'my-page') { // ** ADDED **
        $link['title'] = check_plain($link['title']);
      } // ** ADDED **
    }
    $link['localized_options']['html'] = TRUE;
    $link_text = t('!local-task-title!active', array('!local-task-title' =&gt; $link['title'], '!active' =&gt; $active));
  }

  if (arg(0) == 'my-page') { // ** ADDED **
    $link['localized_options']['html'] = TRUE; // ** ADDED **
  } // ** ADDED **

  return '&lt;li' . (!empty($variables['element']['#active']) ? ' class="active"' : '') . '&gt;' . l($link_text, $link['href'], $link['localized_options']) . "&lt;/li&gt;\n";
}