for example, could they copy paste id tech tech 5s rendering and put in the smart (smooth movement across random terrain, basicaly parkour) system from brink with some modifications to allow it to be implemented with the acrobatics skill?
They could. But copy&paste stuff from one project to another is no easy task and would take a huge amount of time and in the most cases just not be worth the effort.
I mean, mixing a ferrari and a train into a new vehicle, how easy would that be?