Here's how the WARN Act adresses that.
An employer also must give notice if the number of employment losses which occur during a 30-day period fails to meet the threshold requirements of a plant closing or mass layoff, but the number of employment losses for 2 or more groups of workers, each of which is less than the minimum number needed to trigger notice, reaches the threshold level, during any 90-day period, of either a plant closing or mass layoff. Job losses within any 90-day period will count together toward WARN threshold levels, unless the employer demonstrates that the employment losses during the 90-day period are the result of separate and distinct actions and causes.
So if they lay off 500 people in total, not just from any one group, within the 90 day period the WARN applies.
What I'm wondering is if they offer the VBR again could they get the numbers below the trigger?