I could have sworn this worked differently in previous versions of iOS, but as of iOS 4.0 it looks like my app\'s keychain items are not removed when the app is removed. How
If you do a secure wipe of the device, then you may get a fresh keychain.
I was sad to found out that this is not the case anymore, the keychain won't persist anymore since 10.3.
See my reply here.
As answered here, and somewhere else (I can't remember where I read it), the keychain will persist even after the app is removed. I am almost positive that the keychain isn't cleared unless you explicitly delete an item in it.
It persists even after app uninstall. For an enterprise scenario, you may configure n use MDM solution to control the device keychain.