Anyway, one of the rooftops - the more open/less cluttered one - is on top of I-Feng Mansion at the end of the previously posted Mei King Street in To Kwa Wan. All of the following shots are actually on I-Feng Mansion's rooftop.
View to the northwest
The box like structure (with ladder) top left of the upper picture here seems to have been a prop because I can't see it on GoogleEarth, although the other detail can be clearly seen. I suspect it was the bit that was shot up later in the scene, but I can't remember...
The above pictures are looking north(ish) moving NW to NE. The high rise at the back (right) are 'Grand Waterfront' near to the Ma Tau Kok piers.
Finally a view looking pretty much westward towards to green of Ho Man Tin at the back. I think the problem was perhaps logistical - the original rooftop over in Quarry Bay is completely cluttered with illegal tin huts and to remove them all would mean compensating lots of people for the (temporary) loss of their homes/shacks. Moving the actual action over to a more open rooftop probably saved a fair amount of money and hassle.