I could see that if the ballast or the wiring was installed too close to the ABS wire coming from the hub, you could possibly get inductance in the ABS wiring, leading to false signals at high frequency mixed with the normal signal from the hub.
I would imagine that this would also affect the TCS system as well, since it would rely on the wheel speed to tell the computer if the wheels break loose. I can't really figure out why the power steering light came on though. Did you try unplugging the HID ballasts, or even pulling the fuses ( if your power leads have fuses ) to see if the lights went away?
http://en.wikipedia.org/wiki/Inductance