I think it is important to mention that, though you will have to render every clip, you can in fact drudge through a project using ProRes 422 and FCE. Is it ideal? No. But, if all you have is Final Cut Express 4 and you have to do a project with ProRes 422 footage, it can be done.
This is my unfortunate case. I first read that FCE wouldn’t support ProRes and was majorly stressed. Upgrading was not an option for me.
After looking further into it, I discovered that I could still import the footage edit and export the mov, I just had to sit through the rendering process.