I love you a little bit! I'm not sure how well it will pick up the items as they fly pretty far but this is certainly a better solution than a lot of the other I've seen. I think if it's moving underground then the items (for the most part) should stay in the 3x3.
The unknown blocks are from power converters. There's a BC consumer, an energy bridge and a universal charger. Basically it charges the force drill inside the dynamism table. The force drill is great as it can be enchanted with silk touch and fortune.
further investigation seems to show that the game only crashes when the carriage is stopped. I copied the MC window code as it seemed to show a little more info http://pastebin.com/Gbzy9MMY