ABS, like its name suggest, assists the driver to retain some form of control of the vehicle and prevent wheel lockup. Overall, the person behind the wheel will still need to control the steering wheel to avoid lose of control.
Dun forget, ABS also depends on other factors and is onli as good as the tyre u use, the pressure, brake pads, brake fluid, you use
Most modern cars especially continental ones, combine ABS together with EBD or otherwise known as electronic brake force distribution. Whether ABS engages also depends on the sensors. It will be activated at the moment the sensor senses that the tyres have no traction, ie. skiing. This can take place at high speeds sudden braking or even normal braking but on wet or oily grounds.