In my experience of over two decades in law enforcement and watching, spec'ing, and reviewing government acquisition programs, many sellers will help an agency write the RFPs - Harley Davidson, Kawasaki, BMW, Honda did it for motorcycles; Ford, GM, and the various iterations of Chrysler for patrol and specialty autos/truck/vans; Beretta, Glock, Heckler und Koch, Smith & Wesson, Colt, etc. for firearms; Blauer and Fecheimer for uniforms; Federal Signal, Code 3, Whelen, etc. for lighting equipment; and yes - Motorola, GE, etc. for the comm gear.
Public safety executives are often the deciding factor in gear. The RFPs reflect their biases for stuff that they started out their careers with - even if it is not state of the art a generation later. Example - we got a California police chief who started in the business in the 1970s. At the time, the Dodge Monaco and the Plymouth Fury were popular police packages. When he arrived and discovered we had Fords, he vowed to change that to Dodge Charger, even though the cars were not even on the market yet. Our experience with a few Dodge Intrepid police pkg units with V-6 engines was terrible. Fleet services begged us not to buy them, but he got his Dodge Chargers. That was a costly mistake in early days of the Charger. He only lasted a few years, but because few liked them, those Chargers weren't driven and they hung around for years.
RFPs can be a blessing against the bean-counters who refuse to buy quality gear because a Midland portable was $200 less per unit or a curse when someone who has no expertise in the use, durability, and maintenance of the gear picks it out.