I actually played a lot of bass clarinet while minoring in clarinet in college. One main way to play high notes on the bass clarinet is through alternate fingerings. You may know that even on Bb soprano, you can play altissmio notes using the keys you use to play in the throat register, like the keys you use to play G#, A, Bb, B, and C all below the break. So for instance, the thumb, the octave key, and the G# key will produce an altissimo D.
This group of fingerings sounds bad on Bb soprano, so they are typically used only for trills or rapid chromatic playing. But on bass clarinet they can sound excellent, even better than the traditional altissimo fingerings on some instruments.