I faced the same issue while submitting the app using Xcode 4.6. It does not recognise the icons with dimension 120x120, 58x58, 29x29, etc. So when I tried to add these icons into the info.plist and submit the app for review, Xcode 4.6 did not allow me to do so. On submitting the app without the above icons, I got a mail saying -
Since, it was recommended and not necessary, I submitted the app anyhow. I added the above recommended icons to the bundle but did not specify them in the Info.plist. I got the same mail again. This time I ignored it and to my surprise the app was accepted.
I wanted my app to run on iOS 5 and above and therefore, I had to use Xcode 4.6 and not the latest Xcode 5 which properly allows only apps for iOS7 and above only.
NOTE: "Starting February 1st 2014 new apps and app updates submitted to the App Store must be built with Xcode 5 and iOS 7 SDK".
I've tried several times, while adding it to plist even changing the file name and I still got that email. Hoping it will be OK.
@Jules rest assured that it will be OK. My app got accepted without those icons. I do not know what they do for the spotlight icons, I assume they simply use the available icons.(114x114 or 57x57)