ContentHandler::exportTransform needs to be called whenever serialized content is written to an (XML) dump. The WIkiExporter class used by SPecialExport and dumpBackup already does this, but backupTextPass.inc, which is used by the dump generation script on the live cluster, bypasses this.
Other maintenance scripts, like fetchText.php, should probably also apply exportTransform. Generally, all code that calls Revision::getRevisionText should be checked.
Whiteboard: u=dev c=core p=8 s=2014-10-28