If you want writeups on scala/java interop, the Manning "in Action" and "in Depth" books have excellent summaries. From scala you need to worry about java annotations, static members and "throws" exception declarations. Java private /protected etc are checked at runtime and compile time. (That's just me copying items out of the "In Action" ToC, but everything's very well documented).

For clojure/java interop, there's also good writeups in 2 Manning books, and also the OReilly and Pragmatic books. It looks like combining them (Scala/clojure interop) would take some plumbing, depending on the specific libs involved but i havent' tried. (And the Manning authors are all pretty far along on 2nd editions of both "Joy" and "In Action")

http://www.manning.com/fogus2/