These things really are cool. They are everything I want a cart to be and more. They use 32Mbits of flash memory and 256Kbits of SRAM which can be allocated in multiples of 4Mbit ROM sized chunks and 16Kb (I think that's right) SRAM sized chunks for use by multiple games that the user can choose from a menu. It's too bad Nintendo never released them in the US.
I've traced the NP menu code and I see that there are info blocks for each game in the cart and I think I've decoded the relevant parts of the info block. That's the good news.
The bad news is I don't think it's going to help at all in programming the carts. It looks like the menu code uses the info in the info block to display the sizes of each game on the screen however that's not where the real configuration is. The real configuration info appears to be saved in the ASIC chip on the cart itself, either in some on board flash or battery backed SRAM (inside the ASIC). The menu code just selects which game is to be run, sends a command to the ASIC to select game 1,2,3,... etc. and then the ASIC loads the config from its internal store, resets the SNES and you're playing the selected game. I can see some activity on the bus before the SNES is reset but it's not from the SNES. I think the ASIC has a microcontroller on it that's loading the configuration at this point.