If i understood correctly, your old radio is now going to pick up more interference from FM capable units??
I used to manage a fleet of fire tankers and tenders out west for a private timber company. Radios are used to keep from meeting other vehicles on steep, winding, mountain logging roads. I remember picking up HAM signals from central America on clear summer days. It was a little annoying and I guess could be dangerous, but I don't think having to buy new radios would be very popular especially if folks learn why.....seems kinda sleezy and potentially dangerous in the short term.