Yes and no. And 300 meters is much worse than 500 meters. 2.4 and 5 ghz isn’t bothered much by the lines, but if your to close to them you might get weird stuff happening to them electrically. Usually tower grounding should prevent anything electrical from getting strange. As far as RF, obstructions in the path will always have an effect, the question is always how much. Being so near one end, if your using a higher frequency like 23ghz, the beam is very short and hitting the lines will have a reasonable impact on your rssi. Shooting between them and if your able to keep its Fresnel zone clear, than nothing will happen. I’m not aware of any effects the em will have on your signal. If your using 5ghz as a backhaul, and your path is directly hitting the lines, and your using a V and H radio, you’ll likely see a reasonable resistance to your horizonal pole. Again though that’s directly hitting the line exactly middle of your path. If it’s in your Fresnel zone, you probably won’t see it at all.