Okay, I needed it at work, and enough folks have been asking, so I made a very small plugin which 'applies' via a monkey patch, the rails changeset of my integration upload patch to the gem version of Rails 2.0.2.
It's available from github, and the details are at http://talklikeaduck.denhaven2.com/articles/2008/04/18/rails-integration-test-file-upload-plugin