Sorry for this going into the weekend. I didn't really get a chance before now...
I apparently fixed the problem I was having with finding tracks, but wanted to make sure it was valid and not just ad hoc voodoo that doesn't make sense from a simulation standpoint.
Long story short:
I traced the problem to SiTrackerHits not being assigned in 'DataTrackerHitDriver', and replacing it with 'TrackerDigiDriver' fixed it.
Brad