I did find a post on their website about QNX being used to simulate Canada Arm use here on Earth. And according to their website, QNX is indeed used on the ISS "QNX Software Systems’ flagship product, the QNX® Neutrino® RTOS, is recognized globally for its performance and reliability. It is used in many mission-critical systems, including the International Space Station, nuclear power plants, medical diagnostic devices, high capacity routers, and millions of in-car infotainment systems."
Freescale Semiconductor and QNX Software Systems expand relationship for QorIQ and PowerQUICC processors
It also seems to present on other satellite networks.
While the PlayBook OS obviously is something built on QNX, rather than just is QNX, I would guess it is still the optimal choice for use on the International Space Station, especially given how easy it would be for NASA and the other Space agencies to develop apps for the PlayBook, due to the number of supported development platforms.