Where else to put them
I blogged about windbelts a week ago. I suggested using them on bridges and tall buildings. I completely forgot about power lines. Like bridges and tall buildings, they already have basically all the physical and electrical infrastructure in place.
How to make them do as much with less
One potential obstacle to large-scale deployment of windbelts is that on order to generate a serious amount of electricity, each installation would need not just one string but many strings. Naively done, you've use one magnet and several coils for each string. This would multiply some of the material requirements linearly.
But there may be a better way. If you're familiar with the acoustics of the piano, you know that the individual notes1 have not one but three strings. The vibration of any of the strings is transmitted to the other two2. This is the source of a piano's sustained resonance, for one thing.
One could use the same principle with windbelts to couple a range of strings together. Then only one of the group of strings would need a magnet and coils, even though power was collected over all the strings.