can you make a clone image using a program designed to image corrupt hdd's? this way you can poke and probe without fear of this garbage collection performing.
That might actually be a very good idea to do before anything else.
I suppose whether or not an SSD will garbage-collect abandoned data after a format would be highly dependent on whether the formatting OS issued a TRIM command to the drive to explicitly signal that the data is no longer needed, specifically TRIMming the entire drive as a whole. I am not entirely sure whether or not that happens during a disk format operation. But such idle garbage collection is only a concern if the answer to that question is yes.
I don't know about other OS but I do know Windows 7 specifically (both install DVD and OS internally) fire TRIM on a format for all blocks in the format. Ironically this was considered a good thing when it was announced (because otherwise a format won't solve various performance problems).