To answer your question! No. When weather or serviceability interferes, day to day policing may go on without air support, so irrespective of the technology you highlight. Policing does not depend on police helicopters.
Whether a fixed wing is a better platform that a helicopter depends on a number of things such as terrain, environment and the type of tasking you want the aircraft to do. That small fixed wing aircraft are cheaper than helicopters seems pretty incontrovertible!
In England and Wales, the police have decided that fixed wing aircraft have an important part to play in providing police air support, so they are pretty much in agreement with your final contention. All that remains is to decide whether the equipment provides sufficient evidence to be used as a primary tool. or whether it is of a quality that can only be used as intelligence to assist in the solving of crime (as appears to be the case with the description of the system in the piece you highlight). Perhaps the biggest issue is that highlighted by Flying Bull. At the moment, most of what we do is targeted to a specific incident, There is an distinct element of continuous surveillance with the system you highlight (one might argue that with the preponderance of CCTV and ANPR cameras in the UK we already have that). However, that 'Big Brother' effect does appear to interfere with the idea of policing by consent! (unless of course the general public, should they ever be asked agree to a system like that being put into operation).