For some reason, your code wasn't replacing references to the updated class names so I wrote the code myself before yours started working again. Odd.

Anyway, there was still an issue with doubled-up names, so I replaced the str_replace with a regex for more precise replacing.

After the classmap replacer processes each file and the Replacer->replacedClasses property is populated, the files are revisited and the changes implemented throughout.

e.g.

class BH_Google_Collection extends Google_Model implements Iterator, Countable

is now

class BH_Google_Collection extends BH_Google_Model implements Iterator, Countable

and

if (!class_exists('Google_Client')) {

is now

if (!class_exists('BH_Google_Client')) {