It just makes common sense to keep radio equipment of any kind separate from a spark producing unit.
That said though, I have tested an ignition system setting right next to a 2.4 system and found it did not affect it. I did this because I read somewhere a spark system does not bother RF systems above 300MHZ contrary to theory. I decided to test it.
Your friends are probably great engineers but I bet they have not worked with the specific equipment we use and therefore will give you a generalized(Safe) answer.
When a spark occurs it shorts out the applied voltage and converts a nice sign wave into a square wave. A square wave is defined as possessing an infinite number of odd harmonics. That would say that all radios would be affected but they are not. I suspect that the resistance of the wires limit the rise time of the square wave to less than 300 mhz. We can limit the rise time to the point that we will not affect a 72mhz system by putting a resistor in the spark plug.