Problem with url-escaped characters

I'm creating an migration from Typo3 to drupal and part of this involves creating redirect paths per node.

Typo3 news items have ghastly urls, that look something like http://server.com/menu/news/news-single/?tx_ttnews%5Bpointer%5D=3&tx_ttnews%5Btt_news%5D=2523&tx_ttnews%5BbackPid%5D=13&cHash=cb598dc81775331968be88f9dc974c90, but in fact most of the query string can be safely ignored and we just use http://server.com/menu/news/news-single/?tx_ttnews%5Btt_news%5D=2523.

So I want to redirect from menu/news/news-single/?tx_ttnews%5Btt_news%5D=2523 to node/12345, however I'm running into problems with those percent symbols in the original path. Redirect module is escaping them and is therefore creating entries that look like menu/news/news-single?tx_ttnews%255Btt_news%255D=882. I get a 404 if I enter the original path, and a redirect if I enter the escaped path.

So, the obvious solution is to un-escape the original path before entering it into redirect mode, right?

This means http://server.com/menu/news/news-single/?tx_ttnews%5Btt_news%5D=2523 becomes http://server.com/menu/news/news-single/?tx_ttnews[tt_news]=2523. And when I enter this and then view the list of urls in the UI I see urls that look like http://server.com/menu/news/news-single/?tx_ttnews%5Btt_news%5D=2523, just how I want them to be. Yay, right? But clicking on these URLs gives me a 404 and entering the URL with the square brackets also gives me a 404.

So, for some reason, the unescaped url seems to not work at all.

What gives? How can I work around this?