Thanks for the swift reply!
Just to clarify the tension tower - here's a picture of how the insulators are arranged: http://upload.wikimedia.org/wikipedia/commons/5/56/Abspannmast_Detail_20130414.jpg
As you can see, the insulators are hanging, but not statically. They hang down in the same parabolic curve as the cables. Additionally, they have a bridge cable below. Of course, it could be possible to simply model these as part of the pole, but depending on how much the cables hang through, it could look odd.
Just one question about performance: Think of a line of about 20km with an average pole distance of 400 meters (50 poles with 8 cables). See any issues with that scale?