AI does use the 0 turn arty at the start. I have found it very accurate when I'm in the defender or less often in the delay mode of ops. I don't know if this is by chance or my habit (Which very recently I stopped doing under those circumstances.) of lining up my troops "on the line" as I tend to play a more aggressive layered defense on the move and a delay more like a meeting engagement.
In all other circumstances I'm on the line, so I don't know if you will, that the AI learns from this. It has been my experience that the AI will usually have one or two arty observers as a core unit as they are hard to find and kill once found, so this tells me it's an "experienced" unit.
The AI does an excellent job of deploying units such as observers, MG's, ATGW teams, tanks and snipers in over watch positions with good LOS in assigned areas.
You have to factor this in as you move about or you'll ask yourself "
What just happened there?". It still happens to me and is one reason I really love playing this game, because it can be so unforgiving.
AI will adjust it's fire missions to take out perceived strong points and at times along your LOA as you move up.
As Andy has pointed out the AI will advance up everything after a certain point, it's usually a good news situation for the player when you start seeing SPAA and SPATGW coming into the battle zone proper.
Another
more unfortunate indicator (Actually before the above point.) where the AI assumes that some of it's units or its LOA has reached a certain point behind your lines that it drops some of it's artillery way behind your
actual lines, usually concentrated on your victory hexes. This is a horrible waste and where to some degree the human player has a
perceived advantage.
Depending on the AI country though, this could also mean it's softening up the area for a helicopter assault on your victory hexes as well.
Don't let your guard down in the above case, especially, if the AI is Chinese or Russian to a lesser extent.
Seek and Destroy all Arty Observers and HQ units as you find them accidently and or by active search.
Regards,
Pat