Nice article doug brooks.  We need more studies such as that one. 

However, may I suggest that this may also have something to 
do with the circuits within ICs.  A signal on a pcb will 
experience some coupling with the nearest plane, and the 
transistor circuit within an IC may be referenced to one 
plane or the other.  Some IC logic families reference ground
in their transistor circuits, and some reference vcc, and some both.
It may be possible if there is coupling between a signal and 
a plane, a device might not perform properly do to the transistor
circuit looking at the wrong plane.

There may be some cases where something outside the transmission
line may have an issue with the plane our signal is closest to.

Evan though signal coupling to different planes may be an issue, I
have not seen this problem personally.  This may be something not
to worry about unless the engineer expresses some interest in 
routing the signals next to a certain plane.  

      
joez
CAD Engineer
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