However, after analysis of the Windows event logs, it looks the BSOD was coming from repeated errors from the NVIDIA driver (Event ID #14, which Windows complains it has no description, and it comes from nvlddmkm.sys). This error starts piling up several times at once, and in frequency of several hours. After the number of error reaches some higher count, Windows bugchecks with a MCA exception.
As I patched the registry to force PCIe 3.0 x16 speed of the TITAN card, I now reverted to the PCIe 2.0 speeds to see if the issues are going to persist - as it might have something to do with PCIe training.
I also noticed that the ASUS BIOS #5004 does not contain the latest microcode update for the IvyTown CPUs (built-in version 40C), and I know that the several subsequent beta microcode updates solved quite a lot reported sightings, so usage of Ivy Bridge EP with Z9PE D8 WS is still a "beta" experience.