The frequency used lies in the 'short wave' and is the subject of some unsuccessful lobbying by radio hams due to interference on that band.
The EMC Directive of the European Union requires that:
Equipment shall be so designed and manufactured……..to ensure that ……the electromagnetic disturbance generated does not exceed the level above which radio and telecommunications equipment …… cannot be operated as intended (Essential Requirements (1) in Annex 1, relating to Article 5 of the Directive)
Furthermore, although the PLA units, as measured by RSGB and other test houses, are helpfully notched to minimise interference in the amateur frequency bands, they nevertheless produce conducted emissions which will result in interference across much of the rest of the HF Radio Spectrum. The conducted emissions significantly exceed the limits defined in the benchmark relevant international standard CISPR22 (Harmonised EU Standard EN55022).
full article here on the RSGB web site
Power Line Telecommunications (PLT) news page | Radio Society of Great Britain