>>Tacitus, Book 15 Chapter 44 (at least in my Oxford edition) mentions Christ by name and says he was executed by Pontius Pilate during the reign of Tiberius.<<

All he did was explain what Christians believed. He's allowed to do that and not be accused of believing the story, isn't he? In fact, he didn't believe the story and he made that clear. So, his info obviously did not come from historical sources but from Christian literature he could have gotten anywhere.