jack, I got some good news and some bad news.

the bad news: the native carrara pz3 file importer is gonna screw up yer stair-climbing animation,
but it's easy to import it and then time-consuming to tweak it back into shape.

the good news:  carrara can import a poser bvh file and apply it to a figure already loaded
from a carrara runtime, with some tweaking.

the best news: transposer can import the pz3 file/animation (see att. gif), provided one pays
attention to details which may be described in the transposer manual (if any), which I haven't read.