One of the calls made by Brad in the early morning of 7/12 (around 6:30am) pinged off the tower closest to the location of Nancy's body...within a mile it looks like. Kurtz was trying to get the AT&T guy to say that the actual tower was located somewhere else, but the AT&T guy could not testify to that.
This is BIG, imho. It physically puts Brad very much south of his home, south of HT...south of anywhere he claimed to be that early morning. It put him closer to the body location than either his own house or HT!
I don't think they can rely on the cell tower data too much. The AT&T guy basically admitted that location isn't the only factor that determines what tower you use, only more likely. This was demonstrated by showing all the towers Nancy hit on July 11th.