Gee Boiler, that is similar to the simulations I ran when designing the XTB-II output stage. I used several parallel circuits on each phase with different lengths and loading. And I sprinkled around a few capacitors to simulate distributed capacitance and signal suckers. The powerline works very well at 60Hz, but becomes a very complex distribution network at 120KHz.
I agree things can get very complex very quickly using L-C distributed components. I'm guilty of "simplifying" complex impedances with real equivalents (ignoring phase).
One of the things that I am lacking is a good output stage model. I played with this for awhile, but my results were less than satisfactory. Would you be able to provide models for your XTB and perhaps the CM15 or CM11? I have schematics for both the CM15a and CM11a but lack the spec's on the output transformer.
The discontinued ESM1 does display powerline noise. However, its sensitivity to noise isn't that good. For example, that infamous Cellet charger can block most transmissions on a circuit, but the ESM1 displays only one flickering bar from that unit. The multi-CFL "noisemaker" I use for testing the XTB-IIR AGC generates a lot of in-band noise, but doesn't even light up one bar on the ESM1. Basically, if the ESM1 shows even one bar of noise, that circuit is probably toast for X10 control.
I'll agree that the ESM1 can provide both false positives and negatives (noise). I have a Leviton HPCRF that will light up 1-2 bars on the ESM1 with no appreciable effect on communications (haven't put my Oscilloscope on this). It is, nonetheless, a simple plug in tool for verifying both X10 signal level and valid X10 communication. Where is shines is in comparison testing of different circuits.
As you yourself have noted, quantifying noise is a rather complex issue. Units react very differently when presented with continuous, impulse, and transient noise. The issue of where the noise is occurring (relative to the zero crossing) also interacts with the X10 modules AGC. Since all AGC circuits are not created equal (I'm still a bit suspicious of the Smarthome firmware based AGC) this further confounds analysis.
Being a lazy person at heart, I continue to reach for my ESM1 when I have a question regarding noise/level. If that doesn't answer the question, only then will I break out the oscilloscope. Of course, I am looking forward to upgrading the ESM1 when a particular member of this forum releases his analyzer. Maybe then I can leave my oscilloscope at work (where it's rapidly becoming communal property).
Boiler