I've had the opinion for a long time that if you wear a uniform for some company while at work, or drive a vehicle that has a companies name on it you work for that company. Now, the NLRB is coming around to that view it seems.
http://www.npr.org/2015/08/28/435415990/nlrb-ruling-could-pave-the-way-for-fast-food-unions
http://www.npr.org/2015/08/28/435415990/nlrb-ruling-could-pave-the-way-for-fast-food-unions