Threadstarter, you didn't mention which radio was affected. AM or FM?
I too have t-8 fluorescent fixtures in the shop and every time I turn them on it practically knocks out all radio reception except for the local channel.
I don't care if a ballast or driver is class A or B it should plain never interfere with radio frequencies to that degree!
Something does need to be done about it, customers also complain of it happening.
Generally, the worst offender is PWM LED driver. They control the LEDs by rapidly mashing the gas pedal and letting off which actually lets them squeeze out a better lm/W performance, but generally not able to meet FCC regulations for residential use.
Where the interference occurs depends on the frequency of emissions vs the frequency of affected devices. AM radio, FM radio, VHF and UHF are affected by different bands. FCC part B ballasts are specifically intended for residential use where they're meant to co-exist in close proximity with radios and TVs.
There are special lenses or fixtures that use a tinted lens kind of like very mildly tinted windows to further reduce RFIs and used for recording studios and such. Magnetic ballasts are still available new and legal for special applications such as recording studios and medical facilities with sensitive equipment.
The first thing I would check is the grounding between the ballast and fixture, fixture grounding, and roof and metallic building structure grounding. Having all the wires run in grounded metal conduit can help contain radiated interference and conducted be mitigated by a suppression device on the branch circuit.