It's been 8 years since I flew the Bus, but I believe the jet will pull-up (autopilot) if it thinks it is going over redline, whether that is IAS or Mach.

The A-320 uses a "soft-cruise" alttitude-hold feature where engines are held at constant power, and minor airspeed deviations are corrected by small climbs/descents of up to 150 ft-ish (exact number escapes me). It is supposed to reduce fuel-consumption, minimize engine failures (supposedly, most occur during thrust-changes), and for passenger comfort---they don't hear changing engine sounds. I found it worked well; the climbs/descents are so suble that passengers (or pilots) can't feel it---you have to see it on the gauges.

We were cautioned that at high gross weights, flying at FL390 (highest-rated altitude was FL391 or 393; can't remember) was ill-advised. Why? Because if you hit, say, mountain wave suffiecient to initiate Alpha Protection (ie, a stall warning), the autothrottles would go to TOGA. However, that might make you go faster than Mmo, and the jet would pitch-up to arrest the over-speed. This would re-trigger the alpha-prot, and round and round it goes. AND, you could go above max-rated altitude.

Solution was to disconnect the throttles and autopilot.

Earlier in this thread someone said the throttles don't move. True--only in autothrottle. When hand-flying the throttles, they work just like a Boeing.

Pretty sure the A-330 works the same way.