Charles,
I don't think that's viable since it might require access to the other apartments and other buildings which might make a schedule hard to arrange. I've got people I can call on if it were critical but there are two 4-unit apartment buildings and one (large) single family residence sharing the utility transformer.
I spoke with the lady downstairs and she can't think of anything new she added. I should be able to catch the other tenants this week.
If I can't track it down it's not a major problem. I've only lost one X-10 controlled device and I can live without it.
It's more the challenge of solving the mystery that interests me. If you look at the scopeshots I published you'll see that it appears to be non-random.