There is a BA training guide here
http://www.737ng.co.uk/a320training.pdf.
At p14:
"If an overspeed occurs, perhaps because of a sudden unexpected increase
in headwind, the autopilot will disconnect, auto-pitch trim is frozen and
overspeed protection will activate. The auto-pilot disconnect aural
warning will be masked by the ECAM overspeed warning. Spiral static
stability is reduced to zero bank and the maximum bank angle is reduced
to 45°. As
the speed increases, the side-stick nose-down authority is
progressively reduced, and a permanent nose-up order is applied to aid
recovery. To recover from an overspeed, reduce thrust and select
(carefully) speedbrake."
This description relates to normal law. The CVR extracts released by the BEA suggest (without confirming) that alternate law became engaged during the incident. However it is not clear (to me anyway) whether reversion to normal law occurred during the incident, possibly without coming to the attention of the pilots.
Given the incongruous / invalid speed readings, is it conceivable that (i) normal law was resumed and (ii) a "permanent nose-up order" contributed to the difficulty of recovery? Or is it certain that the invalid data or other circumstances would have prevented a "permanent nose-up order"?
Sorry if this has been asked previously.