As someone who's worked for a packager (and a fairly notorious one), I'm having a little trouble here giving the kid a free pass.
Yes, I did work for hire. I do primarily media tie-in work currently (while working on some original stuff of my own). The only way to do media tie-in is to work either through a major publisher (aka Pocket) or a packager who gets the licensing rights and then hires out the work to other people (like me).
It's fun to play in other people's sandboxes, but everything I do still gets vetted, edited and all the other stuff. Even given impossible deadlines like some work for hires get (I think Keith deCandido said he got a Buffy book and had to turn it around a 90K book in 4 weeks and that included edits), there's still no excuse for an author to plagerize even to meet a deadline.
Somewhere in there, the author has to have some intestinal fortitude to say, "No, that's wrong."