USB has been reported to work formatted to FAT32, with NTFS giving the car problems, so don't use that.
FWIW, about 2 months ago I was at the Santana Row Tesla store in San Jose and asked the rep about ipod/iphone USB control. I was specific in noting that in my Toyota, for example, one can connect in this manner but the functionality is quite poor. All you can do is go forward or back on whatever playlist was already open on the phone at the time you plugged it in, with no screen readouts on what is playing or anything. I asked how Tesla planned on handling this.
The rep told me that for both the basic and sound studio packages they were coming out with an interface that allowed a more functional browsing of the entire device with ability to browse the device while connected and with display of song titles and artists and such via the USB, but of course reps have been mistaken on points like this before so who knows.
Cheers.