Anything is possible to some extent, but why take that risk when the odds are against it?
I'm not sure what the risk would be. We have to assume if they were to do it, it would be legal, so lets take that off the table as a risk. So then what are we saying? I have 100K employees (throwing out a number) 20K need to remain employees because of X,Y,Z regulations and absolute needs. But 80K aren't any different than ground at sorting, picking up and delivering, on top of that I won't be doubling up drivers in the field, in fact I would have better coverage with overall less man power and equipment on the road.
I have to assume at this point that each contracted person is money saved, at least directly. I still feel Fedex has a lot to win being unified though either way, but I've been told I'm wrong on this one before.