I am fairly sure it will work - what you are coming from shouldn't matter. And this does not root your phone - it just gives it a different firmware. In other words, once this is done, you will have stock Jelly Bean, you will receive OTA updates directly from Google, but you will not be rooted.
"Flashing" is, as far as I know, just an expression used for "updating" firmware - perhaps because firmware is stored on flash ROM? I'm just guessing here, so anybody, feel free to jump in and rescue me:smokingsomb: