Resolution:
In BWC 5.5, we can use the following url to launch a formflow process attached to a workflow task instead of clicking a link in a portlet like “My Ready Task”:

http://server:port/TIBCOpps/tibco/&ltsite_name>/site/Pages/Forms/Forms+Redirect?
com.tibco.ps.pagesvc.action=portletAction
&secure=same
&windowState=normal
&mode=view
&FRaction=start
&action=redirect  (added for BWC55)
&FRaction.ffName=&ltformflow name>
&rp.username=icdba
&rp.viewmode=Batch
&rp.taskid=&lttask id>
&rp.jobid=&ltjob id>
&FRaction.doneURL=&ltdone url>