This can be done by overriding ecf jobout variable. Here we use date/time to give a unique name to the job out files.
For local job out
task t cron 00:00 11:59 00:10 edit ECF_JOBOUT %ECF_HOME%%ECF_NAME%/%ECF_DATE%/%ECF_TIME%.%ECF_TRYNO%
remote job out
task t cron 00:00 11:59 00:10 edit ECF_JOBOUT %ECF_OUT%%ECF_NAME%/%ECF_DATE%/%ECF_TIME%.%ECF_TRYNO%