Disclaimer: I haven't checked the specs on this version of 4 wheel steering, but if it's anything like Honda and Nissan's versions the rear wheel steering varies:

at low speeds you get a fair amount of opposite steer;
at high speeds with a little steering wheel movement you get small steer in the same direction as your front wheels;
at high speeds under heavy steering it tends towards opposite steer again.

It was always pretty intelligent and didn't do weird things (meaning scary under/over steer things)