So far, I've got an iDevice to stream 24/192 (but the device it was connected to wasn't happy with the output, which is another issue). Streaming high-res definitely works. Playing back greater than 16/48 files on an iDevice will probably depend on what Apple allows in iOS7 and beyond.
By iDevice, are you referring to an iPad or an iPod or both? iPhone??
Do you have any way of determining if it is true 24 bit resolution or 16 bit padded with 8 zeros?