The IOS libraries are irrelevant to the discussion of porting XCode to Windows.
The IOS libraries don't run on Apple OSX, they wouldn't need to run on Windows.
The iOS Simulator relies on those libraries. It doesnt package them within the simulator as it's just that - a simulator. It uses the OS X native libraries. So yes, those libraries would have to be ported and are the most relevant part of the entire conversion.
Do you have any proof of that claim? That would be counter to the design of just about every other cross-platform app - where you isolate OS-dependent GUI and IO code and keep as much as possible identical on both platforms.
Put it this way, if they were using the OS X Native codebase of iTunes, it would be Objective-C code, just like the current OS X version. Obviously this then uses the Cocoa framework.
If you want an OS X, Objective-C based application to work on windows, you have to use another framework for rendering. However you can use the Cocoa basis for Windows with something like Cocatron and GNUStep.
Given that the contents of the MSI package (nor the installed Windows application) show any evidence of them, or any other Cocoa framwork it means they arent using that.
So when you don't use Cocoa (or in iTunes <11's case, Carbon) you instead need to use something like cygwin. However it doesn't use that either (again, you'd see traces of it in the msi binary content files).
The app for Windows is written in C++.
It shares no common codebase. Sure, they would have ported (And rewritten where needed) bits of code and libraries, but it's codebase is not in any way the same. They are just both designed/engineered to the same spec sheet.
It's been this way since iTunes 7.6. It was the same for Safari 4 when that was brought to Windows - it was completely native, just like iTunes.
Have a quick look through the code, and a look around online. iTunes for Windows is a completely different application to iTunes for OS X. Always has been, always will be.
I'm done here. I realise we're still discussing XCode for Windows but come on, we both know that'll never happen so it's a bit of a dead end debate.
Nice talking to you
Edit: Just for clarity as I realise it's hard to read in to what someone types - I'm not being sarcastic.