Here is some guidance my company has provided concerning the P&W equipped 757:
757s do not normally use derated climbs unless airport specific procedures dictate otherwise. This procedure reduces total trip fuel burn, and also reduces the amount of time spent in the N2 speed range in which additional stress may be placed on the HPC.
I cannot imagine company would do anything against the recommendation of Boeing......however, there seem to be many surprises I learn about this industry regularly.