I can see Mr Tai's argument for this being an ex-captive bird. The plumage looks in very bad condition in this set of photos, including considerable damage to the tail and primaries. Some of the arguments put forward by Pete could also arguably support this - a long-staying individual which is not afraid of human disturbance.
Having said that, I assume that this is in fact the individual which has been present at sai Kung for most of the winter, and photographed regularly. See the photos in this post from November, and note the pattern of grey feathers on the forehead compared to the recent photos:
http://www.hkbws.org.hk/BBS/view ... &extra=page%3D1
If this is the same bird, I think it must be a wild individual, as the plumage condition is perfect on the earliest photos. It is currently in moult of the wings, tail and body (note the new inner primaries and inner tail feathers), presumably in preparation for migration. I have noticed moult in late winter on other overwintering Brown Shrikes, but don't remember it being this drastic! The apparently poor plumage condition may also be exaggerated by the bird being wet or perhaps also by it having survived an attack by a predator. Photos taken a couple of weeks ago show it starting to look scruffy:
http://www.hkbws.org.hk/BBS/view ... &extra=page%3D1
If this is indeed a wild bird, it is a good cautionary tale about determining the origin of an individual based only on one set of photos!