Not sure, But I understand that high speed protections on the airbus speed tape i.e the double green horizontal bar are approximately 5 kts above VMO/MMO barbers pole, so once the protections occur you will get a nose pitch up regardless of stick input to reduce speed "HOWEVER" If there happens to be a TA or RA on the TCAS you will have sidestick usage at the risk of getting in to alternate law abnormal attiudes.
So I reckon there has to be a tie in with the Electronic flight control system (EFCS) which includes the 7 computers 2XElacs/3xSEC/2XFac's and the Tcas system allowing input or no input depending on a RA but only if your into protected regimes.
Just my humble opinion, not 100% sure.