Jeremy, two good questions.
Problem is - for us, not for FAST - no white papers or anything like that have turned up yet.
FAST's scientific background is in the NTNU, Norways leading tech university up in Trondheim.
CEO Lervik, Knut Magne Risvik - they all have studied there. To this day they probably hire every talented student from NTNU. (not true - some go to Opticom, FAST's sister company, hehe)
FAST has some time ago started branding their algo. There's a crawler going with that UA - it's called FirstPage
The brand anyhow rarely gets mentioned these days. Many folks optimizing for FAST have repeatedly stated FAST tweaks the algo nearly routinely anyway. While from my experience I can not confirm that, enjoying rather stable rankings, it would make sense: moving targets are harder to hit.
One thing is for sure though: External links are a major factor in FAST's algo. I'm convinced, other than Google those links should be on theme.
Links from the major directories, especially ODP do a lot for a pages ranking.
Rather than themes FAST works with topics. Definately worth studying are the FAST topics displayed on the right hand on ATW serps.
They are based on the ODP taxonomy, classifying sites, and building from there.
Those topics only recently have gone out of beta status, and I think they could need some more improvement.
But yes, FAST tries to establish the main topic of sites and pages.
I will shortly post a collection of some of the threads where we tried to explore the way FAST ranks.