With reference to display of Nav lights on towing aircraft, at LGW a year or so ago there was a trial period where the CAA allowed an exemption to display Nav lights with the TBL Tugs having the extra 'flashy lights'. The trial period was not extended so Nav lights/beacons have to be displayed or officially the towing movement is not allowed to take place. Although theoretically in ATC we should be able to separate the aircraft without the need of Nav lights & I assume this rule is for night, I doubt we'd notice the lights in daytime anyway!