USB Interfaces don't have to be MFI to work with iPads. Just USB 2.0 Class Compliant. I have used several USB interfaces with ipads, you just have to use the Lightning to USB Adapter. So the question is really more if the mixer is USB class compliant, not MFI. Usually if a device driver is not needed to connect it to a Mac, it will work with an ipad. The Auria page describes it pretty well. http://auriaapp.com/Support/auria-audio-interfaces
Also, I don't think you can control the mixer with the UC Surface app via lightning/usb. I seem to only be able to do that over the ethernet/wifi network. but it does work as long as your ipad is on the same wifi/ethernet network as the mixer. but you can definitely record multitrack audio from the mixer to the ipad via usb/lightning.