You can move the anchor point of your 2D layer with the Pan Behind Tool (Ctrl 1 brings up the Tool Palette, or just hit "Y" and the pointer changes to the Pan Behind, then "V" gives you back the pointer when you're done).
There is another Dan expression that's a little easier, and no Nulls needed. It uses the beam effect or the Audio Waveform Effect (like Stroke if no audio used, but will wiggle with the beat if audio referenced), anyway any effect with in and out points. This method connects the in and out points to the anchor points of other layers, like your Pylons. Move the Anchor Point of each Pylon to where you want the wire to connect (Pan Behind Tool if you need to move it).
So to a new Black Solid Layer that’s between the two pylon layers in the layer stack, (make it Comp size or big enough to stretch between the pylons) add the effect Audio Waveform. Add this expression to the Audio Waveform Start Point (Copy the expression (Ctrl C), Alt Click the Start Point Stopwatch, then Paste (Ctrl V)):
target = thisComp.layer("pylon 1");
fromComp(target.toComp(target.anchorPoint));
And this expression to the End Point:
target = thisComp.layer("pylon 2");
fromComp(target.toComp(target.anchorPoint));
This assumes your pylon layers were named pylon 1 and pylon 2. So now the Audiowave form will look like a stroke from pylon 1 to pylon 2.
Note this layer is still 2D, so don't make it 3D. This is from Dan page for make 2D Corene Pin to 3D, it's an illusion, Dan says, but it fools the camera, page here:
http://www.motionscript.com/design-guide/threeD-corner-pin.html
The bonus of using audio waveform is that if you reference the audio within the plug in you could have the wires react to the audio, if you wanted.
It's not as complicated as it sounds, but maybe just using a 2D layer, moving the anchor point and rotating into place is easier.
