>Is the SA-11 TELAR not able to do some IFF on itself?
IMO, the TELAR never does that. On the same second the TELAR radar is activated, the enemy a/c knows it's targetted, so the missile must be launched immediately. Otherwise the target has too much time to do evasive maneuvers and potentially launch a radar homing missile at BUK TELAR.
As a former Skyguard Airdefense Radar operator I can tell you that IFF enquiry is done by the IFF module coupled to the pulse doppler search radar. I can see on my radar screen friend or foe, before I lock onto target with the tracking radar. Civil airliners I had regularly on screen and they are all identified on screen marked as foe!
I don't think that SA-11 is so much different in operations. No IFF = foe
For the rest, I have had usually deployed 3 to 4 spotters which were connected by radio, to tell me if friend or foe