There are no "Trent Specific" limitations upon cruising at or near recommended cruise altitude. The aerodynamic limitations regarding buffet margins apply as in all other aircraft. For the moment, Trent engines must have a Climb Thrust application within the last 2 hours of flight, due to the fuel iceing problems associated with the BA accident.
TO derate restrictions, or to be more specific, Takeoff Reduced Thrust restrictions, applied only to the GE 115 versions prior to modification. In our company (SIA) all GE engines are now modified, and no restrictions apply.
Regards,
Old Smokey