Seems like FedEx would have a legal team that was familar with the Microsoft case (microsurfs). From the sounds of it, the IC's will win.
One of the most basic tests for IC's is: Did the the company mandate HOW the job was done, or just the completion standards? This is what the IRS looks at when they feel companies are looking to avoid paying payroll taxes etc. It's up to the the IC on how they prepare and how they do the job, the company doesn't have a lot of leeway outside of dictating completion standards.
I'll bet FedEx will lose this one.