With poses your working with just the bones of the figure, as long as their internal names are the same then the pose will work across several figures, the only problem being the different bone lengths and default positions in the figures.

Expressions generally work on morphs rather than bones, so in this case you need the internal names of the targetGeom in the different figures to be the same for them to work, add in the difference between Poser figures and TriAx figures and I'd be surprised to find many expressions that work.