[Danny Skarka]"What is the best output format from Avid"
DNxHD QUicktimes. YOu then need to download the DNxHD codecs from Avid.com...and then you can convert the files to ProRes. Or, have the people who use Avid do it...if they can. Warning, there is a gamma shift issue between these two codecs.
[Danny Skarka]" and Premiere "
Premiere doesn't have a codec. I'd have them render out as PhotoJpeg, and then you convert to ProRes.