If they (the boss) knew the job was temporary, then they (the workers) should have known that going in and had been given proper compensation to make up for the looming layoff with plenty of heads up time to prep for the next job hunt.
The formation of a union tells you that the boss did not share that tidbit with the worker. Thus the problem, as the money keeps rolling in for the fatcat for the next decade, the workers who actually did anything of value are starting from scratch at a new job after losing insurance, healthcare, rent and food money, any chance at a raise, etc etc etc.
How else should it work? Almost any other way, is how. With honesty and respect for the people who actually did anything of value, is how.