Using this function you can clone drupal blocks from one theme to another for Drupal 7 only.

clone_drupal_blocks.php

<?php
/**
 * Clones blocks from one theme to another.
 *
 * @param $original
 *   The machine name of the original theme.
 *
 * @param $new
 *   The machine name of the new theme.
 */
function _clone_drupal_blocks($original,$new) {
  // Get array of all blocks assigned to original theme
  $sql = 'SELECT b.`bid`,b.`module`,b.`delta`,b.`theme`,b.`region`,b.`status`
          FROM {block} as b WHERE `status`=:status AND theme=:theme';
  $result = db_query($sql, array(':status'=>1,':theme'=>$original));
  $blocks_orginal = $result->fetchAllAssoc('bid');

  // Get array of all blocks assigned to new theme
  $result = db_query($sql, array(':status'=>1,':theme'=>$new));
  $blocks_new = $result->fetchAllAssoc('bid');

  // Iterate over the original blocks to check to see if the new theme has a
  // similar one.
  foreach ($blocks_orginal as $block_original) {
    // This is basically what makes the block unique.
    // The theme sas's unique key
    $key_original = $block_original->module .
               $block_original->delta .
               $block_original->region;
    $search = false;
    // Iterate over the new theme's existing blocks
    foreach ($blocks_new as $block_new) {
      $key_new = $block_new->module .
                          $block_new->delta .
                          $block_new->region;

      // Money maker right here.
      // If we find the key exists in both arrays, just break out of the iteration
      // If this key doesn't match ever, then we need to update the database
      if ($key_original == $key_new) {
        $search = true;
        break;
      }
    }

    // If the $block_original isn't enabled on $new, lets create/update it
    if ($search == false) {
      $result = db_query($sql.' AND module=:module AND delta=:delta',
                array(':status' => 0,
                      ':theme'  => $new,
                      ':module' => $block_original->module,
                      ':delta'  => $block_original->delta));
      $blocks_new_disabled = $result->fetchAllAssoc('bid');

      // In database, needs updating
      if (!empty($blocks_new_disabled)) {

        // Only expecting one result, and that result is keyed on bid.
        $bid = key($blocks_new_disabled);
        db_update('block')
          ->fields(array(
            'region' => $block_original->region,
            'status' => 1,
          ))
          ->condition('bid', $bid, '=')
          ->execute();

      // Not in database, new
      } else {
        // Grab full copy of block to be cloned
        $sql2 = 'SELECT *
          FROM {block} WHERE bid=:bid';
        $result = db_query($sql2,array(':bid'=>$block_original->bid));
        $block_original_full = $result->fetchAssoc();
        // Insert a new block definition for our theme that includes a complete
        // copy of the original block
        db_insert('block')
          ->fields(array(
            'theme'      => $new,
            'status'     => 1,
            'module'     => $block_original->module,
            'delta'      => $block_original->delta,
            'region'     => $block_original->region,
            'weight'     => $block_original_full['weight'],
            'custom'     => $block_original_full['custom'],
            'visibility' => $block_original_full['visibility'],
            'pages'      => $block_original_full['pages'],
            'title'      => $block_original_full['title'],
            'cache'      => $block_original_full['cache'],
          ))
          ->execute();
      }
    }
  }
}