It is in the single-letter configuration parameters in front of your filename for your file reporter. In the example it is:
<filereports>WDF TestSuite.txt</filereports>
These config params are described here:
http://doc.scalatest.org/2.1.5/index.html#org.scalatest.tools.Runner$@configuringReporters
The one you want is the D, which enables the durations to be printed out, so:
<filereports>D ProductionCommons.txt</filereports>