Well, normally they tend to keep their SAMs some hexes from their map border, though in a final rush they may want to take tem along... Remember that many SP-SAM can't shoot on the move, and are pretty useless in that case
In real life, AFAIK the Soviet doctrine was one SPAA battery per armored/mechanized regiment (3/4 battalions); with mixed SAM and AAG (nominally 2 sections of 2 ZSU and 2 sections of 2 SA-9/-13). Guess they could (limitedly) despatch these, so I generally put 2 ZSU, sometimes +2 SAM per battalion in game. In mech/arm'd infantry battalions you also have a SAM platoon with 2 to 9 MANPADS teams in 2 to 3 BMPs or BTRs (same model as the main troops), plus in theory at least one spare MANPADS launcher in one BMP per company (that is featured in the game with SAM support sections or separate SAM teams with the cmp. HQ squad).
I don't know about the heavier mixed AA battalions that are said to come up in the late 80s, with 2S6, SA-15 and infantry SAMs pasted together. Probable they didn't manage to build many of these.
In the pre-ODS Iraqi army I think they used to deploy one ZSU platoon per mechanized task force (battalion-sized). Lok at the tutorial scenario for this, you'll have a fair portraying of Iraqi battalion organization.