Tim if your RB is picking them up then they are already MODE-S, if they are showing them in the list only then they are just MODE-S but not ADS-B out.
ADS-B out supplies additional information such a position which enables the aircraft to be plotted by RB. At the moment there is no date for compulsory ADS-B (AFAIK) but there is a date for compulsory MODES-S for the big guys it is October 2009 and for GA it is March 2012.
So you will be able to see them in your data grid but not necessarily on your map...
unless AirNav introduce something like multilateration to RB (see the PlanePlotter website for an explaination on how this works).