The simulation has a sector-control, which disables non-visible sectors and regulates also different LODs. In average there are about 3m triangles visible. At the minimum 2m and in high peaks up to 4m triangles. This value isn't always the same, as the simulation looks different every time you start it because the positions of all trees, stones and grass are randomly generated. The sum of all items in the scene together without sector-control, LOD and instancing is calculational 55m triangles.
On our machine (i7 2600K, Geforce GTX560) at the university, where I captured the videoclips, it gets about 40 frames without capturing