Reconstructing the sequence of events will be complicated. All ATC radio transmissions are recorded, so it'll be easy to establish a timeline. If the Swiss accounts are accurate, the Tu-154 pilot didn't respond to the first two calls to descend. The CVR should show if the Tu-154 was tuned to the wrong frequency or if the radio call was blocked by static. Aircraft radios still use AM, so they're sensitive to static and interference.

It'll be harder to reconstruct what the TCAS systems were indicating. I don't know if the TCAS systems have voice synthesizers that could be heard on the CVRs, so if they don't, the only thing the investigators might be able to reconstruct is what the crews said to one another. TCAS systems communicate with one another, but it's possible that a software error caused both systems to direct the pilots to descend at the same time. When it comes to software, flaky stuff happens all too often.