Private investigators go undercover in the company? This sounds like it could be the plot of a movie! It also sounds like it could be kind of fun.
You know, getting inside scoop from the inside? The private investigator would definitely have to have some kind of knowledge of the business though. It seems like they would have to go through the hiring process and actually get hired just like anyone else.
I think this would probably be the best way to get information though. I know most places I've worked are much different on the inside than they appear to an outsider!