There should be an entry in the Southwark planning database (see council website) for planning permission which will have the exact usage on it. Most probably a combination of SPECs (as they have on either end of Tower Bridge) and Congenstion charge cameras. The "loudspeaker" things look like infrared lights, used for nightvision in conjuntions with the low light black and white camera's for number plate reading.
They are probably there to scan pedestrians for 'bad' thoughts. Maybe the plan is to link them to the Inland Revenue's taxation database and add the tax demand to your parking tickets. Maybe they'll link up to the domestic waste penalty notice database and kill more birds with one scan.
Sorry, must pull the blinds down again, the pains are returning.