Rewrite id of a exposed filter block?
To rewrite the ID of the block (if you really want to), you would either use a preprocess function or a custom template file. 

Looking at the preprocess function for blocks template_preprocess_block() found here.

https://api.drupal.org/api/drupal/modules!block!block.module/function/template_preprocess_block/7

You can see how the ID is created: $variables['block_id'] and what the theme suggestions are: $variables['theme_hook_suggestions']

You should be able to create a function in you themes template.php as follows:

function mytheme_preprocess_block(&amp;$variables) {
  if ($variables['block_id'] == 'old_id') {
    $variables['block_id'] = 'new_id';
  }
}


However, with a filterblock, there might be some special relationship to the view that might be damaged, I'm not sure, but either way, you do not need to use Rules.