PBS might work at FedEx if we could use it ONLY on VTO lines in some sort of real-time or near-real time trip selection system.
I always thought it would be good if the VTO line holders were awarded their trips in sequential order AND those trips were removed from open time as they are selected in real time. This would allow junior guys to see what's available in the leftovers. Again, I don't know how it would work and I would ONLY believe it would work with VTO. But it is 2011 and I'm sure there is some sort of real-time technology and/or method that might make it feasible.
If you really think about it, the current system of drop/add and conflict resolution is a hybrid/bastard child of PBS. You knock a trip out for training, you get your pick of trips (in seniority order) AND you know what you got soon after the window closes.