I worked for a contracting company @ HP in Boise. Issue here is that the people who are suing(Adecco, VeriTest, Manpower) are not contractors. They are employees of their respective companies.
The companies(Adecco, VeriTest, Manpower) pay the paychecks, the employees just happen to work at an HP building. The story would be different if these people were independent contractors, contracted directly to HP, but they're not.
Not to mention, the people quoted in the article no longer work for any of those companies... I'm wondering why they left employment in the first place.