Mac OS X isn't a BSD-based Operating System. It's a mach-based kernel (XNU) with BSD userland. The userland stuff likely wouldn't even exist on the iPhone.
I don't think it really looks like Aqua, either.
IMHO, the iPhone is likely running a custom kernel (not XNU), with Mac OS X APIs (Core Image, Core Animation, QuickTime, etc) implemented on top. A microkernel is really not the right design for such a device. Similar to the Windows NT/2000/XP relationship to Windows CE/Windows Mobile.