Doesn't look like a security camera to me, unless the camera is on the other side that can't see in the photo. The reason I say that is if there is a camera lens in one of the holes in the front then the camera wouldn't see much that high - it's very limited in size and angle. It would also get too dirty in next to no time and record pretty much sod all.
If it is a camera and it's able to see into your garden or your property (or a public path) then they are required to inform you and others that there is CCTV, that's normally done by a sign up on the wall. As far as I know you are fully entitled to expect privacy in your own home and the general public should know as they walk past on a footpath. If you really suspect that it is a camera and it's covering your into your home or garden you can get in touch with the police to try and get it moved. I guess it would explain I guess why they were cagey in telling you what it is.