Here's a weird thing; using a Kurzweil Midiboard for input with Studio One 3.5, I had polyphonic aftertouch (poly AT henceforth) playing and recording with:
1) cymbal choke in BFD 3. Very straight-forward, no odd work-arounds necessary (in fact this was true of everything I mention here).
2) pitch bend in AAS Strum GS-2. I held down a C power chord in the left hand while bending an Eb to an E natural in the right. The power was unaffected (as one would expect with poly AT).
3) filter changed brighter in Strobe 2. Again, held down a chord in the left hand while playing a note and adding poly AT to brighten the LP filter. Again, the left hand chord was unaffected as was desired.
In each of the above cases a data curve was visible on the clip.
In Studio One 4, however, I noted that only number 2 (AAS Strum 3) could be attained (recorded and played back), but I noted something else (and I'm not entirely sure this is relevant, nor can I check Studio One 3.5 to see if this is change): on the AAS Strum GS-2, the midi channel drop-down box is not offered on the left hand of the screen's track listing; on the BFD and Strobe 2, it was. Interestingly the ploy AT data played on all three and, if the drawing is accurate, was recorded. It was not apparently sent to either the BFD or Strobe 2.