Try putting a mobile phone next to a radio and/or a computer monitor. Every time the phone does a little search for a cell, your radio will crackle (assuming it's on of course) and your monitor will flicker. It gets worse if there's an incoming call or text.
So interference is real enough. They way it can affect different systems though can be an unknown quantity; it some cases it may, in others it may not. But it's not entirely a myth.
Cheers
Whirls