That's from maybe 8-10 years ago when magnetic ballasts were starting to be phased out for the so-called "digital" ballasts - which are basically just switched mode supplies. Magnetic ballasts rely on a big old laminated core so you start running into increased losses maybe 5 years into the lifespan.
The problem with the "digital ballasts" originated because they used to run at a few hundred kilohertz and the output cable wasn't shielded & given you're dealing with a highly inductive load then "stuff happens"
That's what happens when things get designed by amateurs.
Having had a quick browse it appears things are less problematic now - technology seems more mature, plenty of 5 year+ warranties on ballasts.
A similar problem may be coming/has arrived in your area if your local council is dimming the streetlights because they're doing exactly the same thing. If the cable from ballast to lamp isn't shielded (terminated really) properly then it'll radiate quite a distance.
Edit - I think we've had a similar discussion on here before where I mentioned "digital ballasts" in the context of streetlights, or maybe that was elsewhere
