Adding the following to the UniversalMayaRenderJob.pm *seemed* to do the trick ... though when "view image" from the GUI clicked, it defaults to the most recent render layer (not neccessarily what is printed in the "output" column of the GUI). Each subjob is doing all layers though, so perhaps this is normal behavior.
Regardless, something tells me I fudged this whole thing. Hopefully John, Scott, or Brian might hit this thread up with the proper way to do it. In any case, here's what I added:
elsif ($renderer eq "vray") {
$postFrameCheck = 1;
$successRegex = 'Successfully written image file \"(.*)\"';