I'd be interested in knowing more about how the "safety field test" was conducted and what specific problems were noted. I wouldn't be too surprised if any problems found were related to airspace and potential traffic conflicts with the other NYC area airports. Other high traffic count airports within a few minutes flying time of LGA include JFK, EWR, TEB and FMG. Finding a way to incorporate CDAs into this airspace must be challenging to say the least. However, simply stating that the idea failed a field safety test back in '07 is a rather lame explanation!
Best,
westhawk