About 10 years ago I worked at Smith Industries (now GE) on aircraft displays and such. What they told me about fly-by-wire was that the wire was not similar but exactly a LAN. Two parallel ones. Not sure how the two were arbitrated, but if they didn't show the same command they must have throw-up a warning. The hardware was pure LAN, the data packet protocol was not yer regular TCP/IP though, so maybe there is more error checking, handshaking etc.

The big effort at the time was stuff for the 787 dreamliner. One thing that came back to us was that they were having problems with volt drops because there was so much carbon fibre and less aluminium. The structure was the "ground", and using electrical controls probably meant higher currents than older aircraft too.

An example of how things can go wrong in such a simple process is:
A meeting was called and sent through e-mails though some people heard verbally. The GE takeover had mandated that the e-mail service (security?) was ported through Cincinatti. Which normally worked fine despite the change.
UNTIL daylight saving time or to be more precise the gap between the UK change date and the US one! I turned up only to be told the reason for cancellation.

WELL who'dathoughtit!