I was coming to that
As to the question of whether footwork may apply the eight methods or categories of taijiquan technique, we must examine each aspect individually.
The easiest answer is "yes," because the legs are involved in all of the energies. But, can the legs themselves express these energies? No, not all of them. Lu really requires the whole body. Zhou is the elbow -- although it could be argued that the knee is really the "elbow of the leg." Kao, which is usually translated as "shoulder stroke" seems out as well. However, Dr. Yang Jwing-Ming (YMAA) translates it as "bump," and further classifies it as shoulder-Kao, back-Kao, elbow-Kao, and hip-Kao, which certainly expands the potential of the technique.
It has been my experience, therefore, that of the Ba Shih, the following apply to the use of the legs in pushing and sticking:
Peng, Ji, An, Cai, Lie and Kao. (We'll call knee strikes knee strikes and leave it at that.)
To avoid getting bogged down in lengthy Q&A's, I'll present each as a new topic (just for clarity in the discussion). Naturally, I welcome all questions, criticisms and comments (this is how we develop our mutual understanding). My objective is not to change the art, but to explore it on a level seldom discussed in the Yang style. As I said, the practise is quite common in the old frame Chen style.
Always remember the depth of yin and yang in the footwork:
the active (moving) leg is yang, and the stationary leg is yin; but, the moving leg is also empty (yin) while the supporting leg is substantial (yang). This paradox is the key to unlocking the potential in the steps.