You can read an informed discussion about the Airbus wiring harness problem over at the airliners.net discussion group.
For instance, Baron95 asks these questions:
I would not trivialize this issue. Switching from Cu to Al probably most likely meant increase in wire diameter, increase in connector size and complexity, reduction in the number of allowed connections per cable run, etc.
How many holes and raceways had to be changed because of that?
How many individual airframe parts had holes and raceways going through them?
When EACH one of these parts got redesigned, did it cause any other cascade redesign?
Did they lose configuration control with various versions of these parts making their way into the assembly of MSN001-013?
And CHIFLYGUY adds:
A Boeing (or ex-Boeing) person posted earlier that when they switched to CAD design for planes, they discovered that the CAD software on the market was inadequate for wiring. I wonder if this, at its core, is not the real problem.
Later in the discussion, the coverage by WorldCAD Access (blush) is mentioned.