Thankfully for us, Happy Valley remains one of those areas of HK where much of the older buildings still remains and looking at the current Streetview images we can see the house they are spying on (or at least its front gate) hasn't changed.
The gate is exactly the same! It's either a matching replacement or just very well maintained.
The view up the road (as in the top film grabs) shows that the road's aspect hasn't changed much either, I suspect they are the same trees seen on the film lining the pavement.
This is the current view up the side road where the Hui's had their car parked. The old road sign has gone and there looks to have been some redevelopment at the far end but the walls on both sides haven't changed much.
And finally the view from our intrepid Private I's vantage point looking down the road to the house they are keeping an eye on.