In principle high current DC devices (like a conventional landing light) should not generate any RF interference. You need to worry about strobe power supplies, LED and HID power supplies, "leaking" RF back down their power lines.
So the answer is "it depends". That being said, my wiring is not in a conduit but is bundled together in most places; I have RG400 to the Archer, shielding wiring carry the high voltage pulses out to the strobe, unshielded wires for conventional (incandescent) nav light and HID (power supply at wing tip rib) landing light. This all works with no interference, except a slight increase in background on the radio when the HID is warming up, about 5 seconds.