The notes say(and the xml seems to back this up)
Soviet's artillery gain the ability to support 2 infantry on attack If at the end of their 3rd or 4th turn, the Soviets control Karelia S.S.R. and Caucus (this effect can be doubled to 4 infantry supported if Russia gets Improved Artillery technology)
The xml actually says allied control, not specifically soviet, but thats not relevant here.
See save game history. Turn 3, Russia just took both these countries.
Using latest beta
Pact of Steel 2
Engine Version: 1.8.0.5 Game: Pact of Steel 2 Game Version:3.8
Note I have a screenshot but it wouuld only let me attach one file
It is possible it is done silently and does not check off the technology. I was able to manually add a technology for this. The russians had 2 choices of improved artillery(1 normal and 1 for this thing) after this condition was met. If it is supposed to not show things you already have then this could mean it did not silently give it.