Records on two days (May 30 & June 2)in 2013, one day (June 29) in 2014, none in 2015 (from HK Bird Reports). I haven't seen it on Tai Mo Shan for several years. Last year, I checked two sites on the mountain that were reliable in the past but had no luck. Matt Kwan in his blog "As the Crow Flies" has also commented on the recent lack of sightings of this species on the mountain.
I think the species - for reasons unknown - is virtually extinct on Tai Mo Shan. Seems to be still present on Ma On Shan and on Lantau.
David