Just played two games in a row where an allied CPU didn't build a base building at all (I think they built listening towers, but nothing else).
Map: Stratum P2-8 (3v3).
CPU: Eldar - Casual (possibly all round defensive)
Location; Top left; http://i.imgur.com/YGg0dlD.png
I wasn't sure if the first time was just random chance, but it's the same location CPU twice in a row.