Hi, I made my solution to this problem today and posted it in the code snippits section of the forums
find it here: [url]Fade from one camera to another]
There are no shader’s used, and it completely cleans up after itself (so it’s safe to use hundreds of times without any problems or performance leaks)
It’s relatively simple too, and could be modified to fit specific needs (showing a different scene for instance and fading into that instead of just into a new camera perspective)
Anywho, I hope it’s of use to you, I mostly wrote it for you because I thought it was a curios idea 
~powerpup118