I was backreading the posts in the this forum and came up on this one, I know that it's old however this info may be of some use in the future.

Mike Askin posted info on this subject on his site along with some plug-in's that work in Premier and will do the format conversion from 4:3 to 16:9 and so on, you can read more on his site at http://www.mykaskin.freeserve.co.uk/...s/plugins.html and you can also download his preset files to get the job done.

I've had to use it a few times and it works great, just have to re-render the project to get the effect to work.