It appears that the new S-300s are likely PM1 or even PM2 variants, delivered not from storage but from the 531st Guards Air Defense Regiment, normally located near Murmansk. It appears the unit recently took S-400 deliveries. There is also unconfirmed information that Russian MoD Il-62s flew in crews for the S-300s. Whether they're there to train the Syrians, man the systems themselves, or a mix of the two, remains a mystery.
Note this means we are talking about a Russian military version of the system, with Russian IFFs, and other potentially sensitive equipment. I doubt Russia really trusts the Syrians that much, and the choice of systems suggests that at least part of the operators will be Russian. It would also make sense for Russia to strengthen operational control over Syrian air defense in light of the recent incident.
Россия отправила в Сирию комплексы С-300 из Заполярья
https://imp-navigator.livejournal.com/765626.html
Note this means we are talking about a Russian military version of the system, with Russian IFFs, and other potentially sensitive equipment. I doubt Russia really trusts the Syrians that much, and the choice of systems suggests that at least part of the operators will be Russian. It would also make sense for Russia to strengthen operational control over Syrian air defense in light of the recent incident.
Россия отправила в Сирию комплексы С-300 из Заполярья
https://imp-navigator.livejournal.com/765626.html