From your initial post, it sounds like this problem has existed since the new equipment was installed.
Could it be that there is a fault with the equipment, not necessarily with the radio remote? Presumably you have contacted the supplier/manufacturer?
The presence of the overhead lines could well be a 'red herring',leading to assumptions that interference is the cause of the problem. As has already been said, the figures for field strengths etc are at the 50 hz power frequency.