Ferris, you're right about the TCAS. The transponder always uses SAS 1013. My mistake. TCAS will give accurate readings regardless of local QNH settings
However, I dont understand why you say disregard anything I say when you later in your post agree with me in saying pilots should change altimetersetting passing transitionlayer/level.
Make up your mind
http://www.eurocontrol.int/airspace/...nce_Manual.pdf
Take a look at page 10..