Email response from the CAA
The trial is taking place around Oban in North Argyll using an Unmanned Aerial System whose Vehicle component weighs 1.3 Kg and has the same yellow and black colour scheme as many other police aircraft to aid its conspicuity.
However the UAV is being operated between 50 and 100 feet AGL within line of sight of the UAV Pilot and so it will not come into conflict with any other air traffic. Air Traffic Control at Oban are being notified each time the UAV is flown and if it appears that another aircraft is flying towards the UAV at low level then the UAV will be landed as a safety precaution.
It is not intended that the UAV will be flown in IMC but instead will be flown below low cloud and hill fog, within the height limits mentioned above, that would not permit the operation of conventional police helicopter or aeroplane.