Forgive my hardware ignorance. What is a Sun Fire? I would guess it is a SUN UNIX box. I'm sure you have already looked, but supported Pro/INTRALINK Server hardware requirements can be found on the PTC web site at:
If the Sun Fire configuration meets the Pro/INTRALINK server specifications (hardware and software), then it should work fine.
This is not a sales pitch, just what I've seen as an industry trend. I implement Pro/INTRALINK for companies. I haven't run across many companies running UNIX for their Pro/INTRALINK server(s). There isn't anything wrong with UNIX. To some extent it is still more stable than Windows servers. It is just typically more expensive and harder to find qualified people to administer it. The lack of an earlier reply to your posting may be due to this trend.