Brake help is made completely obsolete by ABS (it's like an extremely primitive version of ABS), but I'm not sure if it's automatically disabled if the car has ABS activated.
You can easily test this by enabling both ABS and brake help and making a setup with strong brakes. Then brake hard at 100% and steer into one direction. If the red brake indicator bar in the lower right corner stays at 100%, brake help is disabled or at least has no influence / doesn't engage.