Hello,
I will give a short description of what the technique is about.
The left hand rotates or pivots on the thumb so one position can expand to a major third on one string as opposed to a major second in other techniques. The books develop the ability to play across the strings in all positions. At times the thumb and finger movement are such that it is called the crab technique because they resemble a crab walking. Accuracy is aquired with less shifting. Thumb position can be used anywhere, even below the harmonic at the octave. French bow grip is generally fluid with a loose and flowing wrist.
There are also several posts on TalkBass if you search Rabbath. Here are a couple of other links about Rabbath and the art of the bow has a video clip of him.
http://www.artofthebow.com/dvd/ http://www.liben.com/FRBio.html
Get some of his recordings and you will hear how musical he is. Hearing him and seeing him live made me want to play with his technique.
I hope this helps,