Just to clarify one thing...
If during flight, there has not been an event which has led to an investigation by a state investigator (AIB), then under law (derived from ICAO annexes), there is no protection of the recorded data. The company may, then, listen to any CVR and examine any FDR data from a flight which has not involved a reportable occurrence or otherwise caught the formal investigative interest of the state investigators.
In some companies, agreements (often involving unions) restrict this.