Not an electrical engineer, but I am a (materials) engineer with several years in the power industry.

Power lines do have EM fields around them. When metal objects move relative to the EM field, or when the fields (power lines) move relative to fixed metallic objects (as on a windy day), then a static charge may build up in them. This charge may be considerable if the field is allowed to accumulate for a long time, and the field may discharge when rider's metal SPD cleat contacts with the ground, and the other is still latched onto the metal pedal/crankarm/frame of the bike.