Not sure if it is a valid strategy, but my idea was to use the commit date as revision number for Clearcase files. Since revision number in CC is not global we cannot rely on it to base the partial changelog, but by replacing it by the commit date, the ProjectStatus will always have as revision the latest commit date.
This way, we can implement in FixedClearCaseChangeLogCommand the method executeChangeLogCommand using the start version by decoding the start revision into a date and using this date as "-since" parameter of the lshistory command. This enables then the partial changelog for Clearcase.
We tested this strategy successfully on our projects. I will attach our patch for this strategy.