As far as I know there is no cradle out yet for the iPhone 5.
On my 750i - 2013
1) iPhone 5 works for music with full iPod menus and art cover only with it's iPhone cable (lightening connector) connected via USB. Apps work also via cable. Phone functions are fine simultaneously via Bluetooth.
2) iPhone Music works via Bluetooth, but only track forward and back show up on iDrive - not art cover or search.
3) I had a "Music" cradle for my 4 from my 2010 - it did not work at all on the 2013, except for charging the 4S. I traded the "Music" for a "Media"cradle and that one works fine for the 4S. Same functions as when connected via Apple connector cable on the 5.
4) Both the 4 (in cradle) and 5 (via USB) are connected and I can switch between them via iDrive (Media Button) to choose the music. The 4 is being used as an iPod only.
Hope that helps