Lacking information. In his book Jesus, Charles Guignebert states that "so long as there is that possibility [that Tacitus was simply repeating the story as it was being told], the passage remains quite worthless." Without more information, which we don't currently have, the passage proves nothing (it can't be used as evidence for or against).
Sourced from Roman archives. In Historical Jesus: A Comprehensive Guide, Thiessen and Merz argue that if the source had been an official Roman archive, one would expect him to have referred to Pilate as a prefect instead of as a procurator (he was not a procurator). They thus conclude that the information Tacitus gives about Jesus was not copied from an official source.
Opposing viewpoints:
Thiessen and Merz (above), while stating that Tacitus provides few details the source of which is unclear, conclude that there was a Jew named Christus who Pilate had executed, and he began a religious movement which was widespread during Nero's reign.
Bart D. Ehrman writes, "Tacitus's report confirms what we know from other sources, that Jesus was executed by order of the Roman governor of Judea, Pontius Pilate, sometime during Tiberius's reign." (The New Testament: A Historical Introduction to the Early Christian Writings)
The writings of Tacitus can be considered as either non-Canonical confirmation or as useless, depending on whether the scholar thinks Tacitus exercised due diligence in investigating the story before writing the passage.
Given that we are lacking key information, and that the passage itself provides very little detail, a determination about Tacitus' diligence in investigating it cannot be made. Any statement which assumes he did exercise due diligence (i.e. that what he said was based on fact) is speculative.