Microsoft have produced a blog post called "Building a Simple App with the Windows Bridge for iOS".
https://blogs.windows.com/buildingapps/2016/01/20/building-a-simple-app-with-the-windows-bridge-for-ios/

In it, they use Xcode to create a simple app and then use VS2015 and the Windows Bridge for iOS to turn it into a working Universal App for Windows 10 devices.

It appears to translate the xcodeproj into a VS project using a utility called vsimporter.

Given how Delphi/Firemonkey creates the projects and then uses Xcode to codesign them, I'm guessing there is no Xcode project created which presumably means this method won't work for multi-device apps created using Delphi?