421 MHz is allocated to amateur radio (often as secondary) only in Regions 2 and 3,
and then often with restrictions (military - such as White Sands, Canada/US "A" Line, etc.)http://en.wikipedia.org/wiki/ITU_region
In Region 1, primary locations of the movie's storyline, is not allocated for amateur radio.Usage by law enforcement or first responders believable, Police Urbaine in movie.http://en.wikipedia.org/wiki/70-centimeter_band
In addition, in the USA -- frequency spectrum between 421 MHz and 430 MHz IS available for commercial two-way radio use in the Detroit, Michigan; Cleveland, Ohio; and the Buffalo, New York areas. These locations are located within the "A" line of USA, south of the Canadian border
This is per 47 CFR Part 90 Section 90.273.