The code in MAME is not from DICE, only a large percentage of the actual circuit layout is common between the too (think of it like roms being common between emulators).
The missing thing here is the schematics from the home pong consoles. While arcade pong was created using off the shelf parts and the schematics are available, home pong had the entire thing shrunk down into an ASIC. It would be possible to decap one and trace it out, but it would be very hard and I haven't heard of anyone doing it.
