Redmine

Short answer: yes.

I also needed to convert from RT to redmine. I also could find no script to do so.

So I wrote one myself.

https://github.com/txcowboycoder/Request-Tracker-to-Redmine-Migration

I would love to make it better, but our implementation of RT is just over a year old, and as such we haven't used nearly the full feature set of it.

Since the state of the script satisfies my companies needs, I have the desire but no test data or time to make the script more robust.

Hope this helps.