OK, so I just downloaded xcode to limit the number of cores used on my dual 6-core Mac Pro. Here's what I found:

I can run the game if I limit the number of cores used to 16 (with hardware multithreading - aka hyper threading - enabled).

I can run the game if I limit the number of cores used to 8 (with hardware multithreading - aka hyper threading - disabled).

Those are the upper limits. If I enable 17 cores (with hardware multithreading aka hyper threading enabled), it crashes upon startup (pressing "play"). If I enable 9 cores (with hardware multithreading aka hyper threading disabled) it crashes upon startup (pressing "play").

Just thought I'd add some more information for your analysis.

Modellname: Mac Pro
Modell-Identifizierung: MacPro5,1
Prozessortyp: 6-Core Intel Xeon
Prozessorgeschwindigkeit: 2,66 GHz
Anzahl der Prozessoren: 2
Gesamtanzahl der Kerne: 12
L2-Cache (pro Prozessor): 512 KB
L3-Cache (pro Prozessor): 4 MB
Speicher: 8 GB
Geschwindigkeit für Prozessorverbindungstyp: 6.4 GT/s
Boot-ROM-Version: MP51.007F.B03
SMC-Version (System): 1.39f11
SMC-Version (Prozessormodul): 1.39f11

Chipsatz-Modell: NVIDIA GeForce GTX 680
Typ: GPU
Bus: PCIe
Steckplatz: Slot-1
PCIe-Lane-Breite: x16
VRAM (gesamt): 2048 MB
Hersteller: NVIDIA (0x10de)
Geräte-ID: 0x1180
Versions-ID: 0x00a2
ROM-Version: 3731