OZBUSDRIVER, I was responding to UNDERFIRE pointing out that all the references to WAAS were not necessarily referring to augmentation capabability, but instead because WAAS units are C146a units which us required for ADSB. That's all.
To be a bit pedantic, the FDE capability of C146a units does not guarantee integrity of position, it just flags if there is not integrity of position. Integrity of position is determined by the health of satellites, the almanac position of satellites, antennae and physical issues of the GPS unit, environmental conditions and potential presence of jamming sources. A C146a unit does not have magical control of these factors to guarantee integrity - but it can flag conditions where integrity of position does not exist.