According to Airbus, they have modified the flight control software so that it is less likely to disconnect in a turbulence encounter(autopilot robustness). It would be interesting to know if this mod is on all aircraft or is just an option.
"Flyby-
wire aircraft
A severe turbulence may lead to excessive high
speed excursion (beyond VMO/MMO) or to
excessive low speed excursion (below ‘alpha prot’,
angle of attack threshold of alpha protection law
activation). This will induce Autopilot disconnection
and activation of the appropriate manual flight
control law (The VMO/MMO protection or the angle
of attack protection that will command respectively
pitch-up and pitch down movement to reduce
these excursions).
In order to keep the Autopilot engaged as long as
possible, flight controls software modifications
have been developed on fly-by-wire aircraft. They
make the Autopilot more robust to disconnection
resulting from a transient VMO/MMO or ‘alpha
prot’ exceeding subsequent to a severe turbulence.
Autopilot robustness improvement in case of
transient ‘alpha prot’ angle of attack exceedance
has been already implemented on all in-service
fly-by-wire aircraft.
Autopilot robustness improvement in case of
transient VMO/MMO exceedance has been
introduced as shown in various flight control
software."