Because power lines are not designed to prevent radiation of RF energy, BPL represents a significant potential interference source for all radio services using this frequency range, including the Amateur Radio Service. Overhead electrical power lines and residential wiring act as antennas that unintentionally radiate the broadband signals as radio signals throughout entire neighborhoods and along roadsides. Interference has been observed nearly one mile from the nearest BPL source.

And a little more:

 Studies by the National Telecommunications and Information Administration (NTIA) show that the probability of interference from a BPL system operating at the FCC radiated emission limit on the same frequency as a typical two-way radio station is essentially 100% 200 to 400 meters from the power line, depending on the frequency. Despite this clear evidence that the limit is too permissive, the FCC declined to impose a tighter limit except in frequency bands used by aeronautical services. This means that unless they voluntarily design their systems for reduced emissions, BPL system operators will have to take expensive, customized steps to correct interference on a case-by-case basis. That may not be possible unless they turn off their systems. Of course, they will strongly resist having to do so. This is why radio operators are so concerned, and why BPL customers cannot be assured of receiving reliable broadband service.

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