ORIGINAL: ram3500-RCU
As these two planes were the only two affected, and they both went down in similar fasion, I am also leaning in the direction of a deliberate act. My brother and I lost a scale Hawker hurricane to a deliberate act from a police car. The two officers denied any involvment at the field, but where overheard to admitt it after a few drinks at a local watering hole. They "just wanted to see what would happen", as they said. Serve and 'protect'?
This was years ago, but I still can't rule out this senerio.
This sounds like one of those old wives tales! I work with police and fire communications and can think of no radio equipment that would be carried in any of these vehicles anywhere in the country that would interfere directly with our RC equipment. Maybe the officers were keying their mics in a joking manner to see if they had any effect but I suspect your crash wasn't related to that. When your plane crashed when they did whatever they did, perhaps they thought they were the cause and got vocal about that when they were well "watered".
The incident in this thread sounds like some kind of a deliberate act but I seriously doubt it came from emergency vehicles. Speculation about military and other causes could be possible but I suspect someone with a synthesized transmitter module to be a more probable cause.