You obviously didnt google it very hard; Google result for ai.tlb
Im not sure by what you mean by AI only buildings. If you mean that only the AI can build them and players cannot then set the techlevel to 11 and include the tag AIBuildThis=yes, however, they will only build one of the building if you want them to build more than one, you will need to add the tag IsBaseDefense=yes and add it to the relevant listing.
This also has probelms as they will build less actual dase defences in preference to building your building, and they will tend to build them on the outskirts of their base (although as the base expands they will no longer be right outside the base)
Im not sure by what you mean by AI only buildings. If you mean that only the AI can build them and players cannot then set the techlevel to 11 and include the tag AIBuildThis=yes, however, they will only build one of the building if you want them to build more than one, you will need to add the tag IsBaseDefense=yes and add it to the relevant listing.
Code:
AlliedBaseDefenses=GAPILL,ATESLA,NASAM
SovietBaseDefenses=NALASR,NABNKR,TESLA,NAFLAK
ThirdBaseDefenses=YAGGUN,YAPSYT,NATBNK
This also has probelms as they will build less actual dase defences in preference to building your building, and they will tend to build them on the outskirts of their base (although as the base expands they will no longer be right outside the base)