Bart:
It happens fairly often, if you count all the times that one developer group fails to get the project launched, and another group comes in and decides to go with a different architect. There are also lots of times where multiple architects will produce a routing on spec [for free] in hopes of landing the job, but someone else gets it instead.
However, it doesn't happen often at all [in my experience] that the client decides to change architects after paying an architect to develop plans. In thirty courses, exactly one of my clients had started with a different architect -- Stonewall started with Tom Fazio -- and exactly one client dumped me for another architect -- Red Hawk GC in East Tawas, Michigan, finished by Arthur Hills. In neither case was the change of architects based on the routing, it was because of other factors.
Brian Sheehy: It's possible to change a routing, but it's difficult. In the case of a links such as Tralee, presumably you would want to return some of the fairways that exist back to nature in order to move them somewhere else ... and that's difficult to achieve. But, it might be easier on an open links site than on a parkland course, where years and years of planting have reinforced the original routing.