john_smith
On the Airbus (not sure if its type specific or not: I suspect not) TCAS will only demand either a 1500fpm or 2500fpm ROC or ROD. Those are the only two possible options for climb or descent RAs.
Do you have an FCOM reference for that? Mine (A320 and330) say that the V/S is optimised to avoid.. and V/S changes are minimised.