As it is the rooftops that these guys are running around make it difficult to pinpoint the exact location but there are a couple of landmarks that give us the rough area. Here are a few of the screen grabs.
I did stitch a few pictures together and came up with the following panorama. The things to note are the Marine Department building with its small white tower almost dead centre (or far left if you look at the screen grab above). This building sat along Connaught Road and Rumsey Street. In fact you can see the gap in the buildings next to it that marks Rumsey Street. The building lasted until 1983 before being replaced by a mall that is now called Infinitus Plaza (formerly Vicwood Plaza). So given that information, and the angle on the street, I can only guess that we are somewhere around Shing Wong St area (give or take a few blocks).
Another interesting building that can be seen is the old Sun Company building at the far right of the panorama. It was a skinny building with a sort of tired rooftop and I believe was a local department store. The building ran along the length of Wing Wo Street and its modern replacement occupies that same skinny plot and is called "Sun House".
Anyway, I'm happy to accept any offers on the actual location (where the camera was) as I think my guess leaves a lot to be desired. By the way, if anyone knows what the large building was between the two I've just mentioned (it would've occupied the site of what is now Li Po Chun Chambers) then please leave a comment.
Before I forget (as I did the first time this was published), there was also a brief shot of another part of the skyline but further to the west over Sheung Wan. The picture below shows the building that Belmondo climbs out of before heading off on his rooftop jaunt. In the distance, fronting the harbour is (behind Belmondo's butt in the top picture) the Sun Kwong Hotel. If you look closely, to the left of it you can just make out one of the chimney stacks of Western Market - the gap between the two being Morrison Street.
I'm not sure what the building is in the bottom of both pictures but it's possible it is the King's College Old Boys Association Primary School (built 1958) on Bridges Street which would make the building we are on somewhere in the vicinity of today's Caravan Court/Kin Yuen Mansion on Caine Road. Corrections or guesses welcome.