OK seem to have most of it figured out.
Didn't realise that the trick was to not access GitHub directly and to point the TrackStudio "root" at the local GIT repository. I presume TrackStudio doesn't do a fetch automatically and that I'll have to set up a cron job myself to keep the local repository in sync with GitHub?
Have found one problem so far. When I click on a changed file identified in the TrackStudio SCM References Revision, I either get nothing in the pop up window or a message like:
fatal: bad object af54e1e17cbeeb442490767e94518138fe16205a
with a URL of
http://trackstudio.dtc.com.au/TrackStudio/SCMAction.do?method=diff&revision=af54e1e17cbeeb442490767e94518138fe16205a&diffURI=com/dtc/sportzman/MembershipCardListView.java&connectionName=SportZmanDesktop