The County of Alameda had a massive layoff about 15 years ago. A lot of folks were laid off who were tenured, but didn't have as much time as folks who kept their jobs.
Money was tight statewide and we weren't getting state support (as we are constitutionally SUPPOSED to be) from the tax coffers, so the County was forced to cut its throat, so to speak. A lot of folks in clerical/finance positions were let go, only to be rehired as temps, but without the medical/dental/retirement benefits.
In the mid-1990s, the unions became very active, especially the SEIU, and demanded that the County do something about the incredibly large TEMP workforce, especially in light of the County having become fiscally solvent and having become engaged in buying buildings and constructing same.
We now have a very meager temp force...and there are strong union-demanded guidelines that have been put into place that make it nearly inconceivable such layoffs will occur again.
Never say never, though.