Courtesy of the Greeks, Israel will not face an unknown air defense environment if Iran gets S-300 missiles:
The Israeli Air Force has used INIOXOS-2015, one the largest annual exercise of the Hellenic Air Force, to prepare for a potential situation where it will have to attack Iranian nuclear facilities by performing missions against the S-300PMU-1 surface-to-air missile system, stationed in Crete, according to Flightglobal.
Even a successful strike might not matter, if my speculation is correct.
Of course, experience against the S-300 would also be of use in a war against Hezbollah if Syria has any deployed to cover Lebanon's air space.
So Israel is getting ready for something. Just in case.