Digging Through iOS Graphical Ressources
blog.manbolo.com
blog.manbolo.com
I've worked on projects at past jobs where the designs demanded that we duplicate the look and feel of certain iOS system APIs and programs to a T. Apple passed those through approval without making a sound about those bits.
On the other hand, Tapbots has had an app rejected in the past for using a clock icon that looked a little like Apple's[1], back in 2009. And that wasn't an exact copy.
We're not going to get an official statement from Apple on this, so the best I can suggest is to tread with caution. Better to be inspired by than to flat out copy.
[1] - http://tapbots.com/blog/app-store/a-well-timed-letter-of-rej...