Sounds like a done deal. I'll bet that there is one of these in the KOP:
http://www.computercablestore.com/Mo..._F_PID948.aspx
As well as some of these:
http://www.dataaccessories.com/rj11.html
Communications protocol is here:
kamocat.com/Jag/SW-RDK-BDC-UG-4201.pdf
As far as CAN being a liability because of single point failure (as opposed to independent PWM line), I'm sure that no one has built in redundant motors so the net result on a cable failure would be the same between CAN and PWM.
Good thing about CAN is that you can monitor motor voltage and current and hence computing a running energy expenditure tally would be quite simple.
Energy = Power*Time = Voltage*Current*Time
Suggesting that this year's game may be about keeping track/minimizing energy resources in pursuit of a more general goal. This allows FIRST take a quantum leap in relevance.