The filename in /ars/tmp looks like a bug. It should be the path and filename where the original file was listed, not where the temporary file lives.
The Load ID hasn't changed much. The old format was:
5559-11-0-10369FAA-17081-17081
AppGroupID-StorageSet-0-DocNamePrefix-MinDate-MaxDate
The date format was either number of days since January 1st, 1970, or the number of seconds since January 1st, 1970, depending on the configuration of the Segment Date field in your Application Group.
And the new format isn't much different.
5559-11-0-10381FAA-20161007000000-20161007000000-5562
AppGroupID-StorageSet-0-DocNamePrefix-MinDate-MaxDate-ApplicationID
Where dates are now stored in YYYYMMDDHHMMSS format (Thats YearMonthDayHourMinuteSecond). The only addition is the ApplicationID at the end, which refers to the internal numeric ID for the Application definition that was used to index/load the data.
There's also an article on the Doc_Name format on the CMOD wiki:
http://cmod.wiki/index.php/DOC_NAME-JD.