Tom,
The Dan Foss type power steering has been around for a long time, and all large off road equipment, farm equipment and farm tractors use some version of this type of steering and it works well and reliable for this application. It is good for something going 20 mph but I would not even consider it for something that is projected to go 500+mph! It is cumbersome, heavy, not very accurate and provides little driver feed back. If you have driven any of the later model farm tractors their steering is quite strange, the position of the steering wheel vs the direction the tractor is going is changing all of the time, this is because there is no feed back between the actuator that turns the wheels and the steering wheel. Kind of weird but you can get used to it at only 20 mph, not at 500.
Looking at Freud's pictures it looks to me that the Treit car is going to use some sort of master/slave system in which they use a standard steering box with the pitman arm connected to a hydraulic cylinder, the master cylinder. The steering box moves the piston on the cylinder and the oil from this cylinder is sent to the slave cylinder that then turns the wheels. This type of steering can be very accurate and provide good driver feed back but it is all in the details of how you do it that makes it work well. They could certainly use electronics to provide a very accurate and responsive system but I think one of the "rules" for the Treit car is "No electronics".
It is going to be interesting to see the details on their system just as it is interesting to see all of the other details on this fantastic car.
Rex