So would the EMAS have saved the day or even mitigated the accident? Unfortunately in this case it appears not.
I think you are wrong in that conclusion, OverRun.
The assumption the aircraft left the runway at 100kts, is just that - an assumption at this stage. Might be faster, might be slower. Lets concentrate on what we know for sure.
If we go by known facts, I think that EMAS would most certainly have saved lives. Being that some of the injured died at hospital or after the crash, we can deduce that the impact speed was right around the threshold of survivability for these circumstances - regardless of what that actual speed was.
That is all that matters in a crash really - how quickly you come to a full stop. Speed is not the killer. If you hit the ground at 250kts but use up 3 miles to stop, then you will most likely survive the impact. But if you hit an unforgiving obstacle at 50kts and take only 1 foot to stop, then you will probably die or at least end up severely injured.
The overrun did not kill in this instance, it was the unforgiving obstacles that killed the occupants. EMAS would have certainly shaved 10 or 20kts of their speed, and that might have been enough to bring them within the threshold of the restraint devices and within the energy absorbing limits of the airframe. Remember that as speed increases, the chances of dying go up exponentially.
Either way, by FAA standards, this runway is illegal unless it has EMAS. The RSA is simply not long enough. And with obstacles so unforgiving like the dirt embankment they hit, IMHO, I would exceed the FAA limits and put EMAS all the way up to the highway shoulder (or even shorten the runway a bit to extend the EMAS strip). This time it was an empty repo flight, next time it might be a full IL96 with Russian vacationers.
Hopefully the Russian authorities, as tragic as this was, take this accident and look at it as a warning of how bad it could have been.