From what I can ascertain only TCP port 135 is open. I don't know the answer to your question but found some useful links here: 1. Link 1 (ISA 2000 topography) & 2. Forum to ask about this type of firewall & 3. Links to discussions opening up ports for ISA 2000 & perhaps 4. Some other links Hope this helps. If you sort it out can you post back & tell us how you did it.

The only other thing I can think of is using Proxy. But I don't personally know about setting it up.