Are there real life counterparts to the characters in the anime? Has there been an official credible reference that there are real life counterparts to the characters in shirobako?

I heard from a friend today that there are real life counterparts to the cast just like there are real life counterparts to the studios in the anime. My friend said that he knows that at least the director and the mohawk production assistant had real life counterparts.
Oh boy, this is going to be a big answer eventually. There's a lot more than I have here so far, but I need to go back and rewatch some of the episodes to re-find some of the references. I'll continue to update this answer every so often as I rewatch the show.

I don't know that there is an "official credible reference" (in fact, I suspect that there is not and never will be such a thing because of how Japanese media tends to pussyfoot around references to real-life people/media/etc.), but some of the references to real-life people are incredibly transparent if you know who they're referencing. 

Miyamori and her four friends don't have real-life counterparts, but many of the other characters most definitely do. Here are some of the ones I'm aware of.



So, first off, Shirobako director Kinoshita Seiichi looks a lot like real-life director Mizushima Seiji (and their given names are eerily similar). I'm told that the director of Shirobako (coincidentally named Mizushima Tsutomu) is buddies with Mizushima Seiji, hence his appearing in the show as the director.



The three Exodus lead voice actors - Nakaharu Mei (Akane), Kayana Mui (Alpine), and Itou Suzuka (Aya) - are voiced by real-life voice actors Nakahara Mai, Kayano Ai, and Itou Shizuka. 





And, of course, veteran director Kanno Mitsuaki, the man behind Avangelion, is none other than the master, Anno Hideaki.