Airbus rudder controls
 

Question about A330/A340 rudder systems:

They were mechanical/fbw hybrid (pedals were mech link, FBW could augment) in the original A330-300 and A-340's.

But the big stretch A340-500/600 and the shorter A330-200 both have a new system that uses electrical signal from the pedals and a backup control module with hydraulic generators to ensure rudder control even if everything else goes dark.

It'd seem to me that production economy would dictate that the new eletro-rudder be put into production on all the models. Is this the case? Is that related to the "E" variations that are sometimes talked about? Is it available as a retrofit to completed aircraft?

Questions, questions, questions...thanks!

--Nick