Yes, USB - Ethernet would definately not work. In the first place, you would need something that supports USB Host. Some PDAs have this, but it is usaully just for something like a flash-disk or card reader or digital camera.
Remember: Ethernet = network. USB = camera/scanner/mouse/keyboard/external harddrive/flash-disk/external CD-writers/printers/etc. So if one port can do so many things, how does Windows know what you are using?? Drivers - you would need smart drivers to "interpret" what the device does and what the signals it sends and expects mean.
Now if Neotel designed something like this from scratch - then it means that they had to write drivers (and probably only for Windows / Mac). Then there isn't going to be anything at the moment that isn't a Windows PC that can understand what language this Phone talks. It wil come in time, but as the other people said, it is much better to use Ethernet - as all Ethernet jacks talk only one language/protocol.