I did a little investigation on this game, and this is what I found:

http://meristation.com/noticias/2000/septiembre/20000904-08.htm

The article is in spanish, here is a translation of the relevant parts:

First they talk about how the arcade crisis is forcing Namco to take extreme measures, and then they say:

"The first (measure) was abandoning the System11 and make games for the ancient system10, much cheaper and less powerfull, with a similar architecture to the Playstation. For this (system10), Namco has presented the sequel to Mr Driller and Truck Kyosokyoku, a pretty standard Truck racing game.

The second measure means the launch of a new board called System246. This board is the same as what once was the system10, it practically copies the Playstation2 architecture..."

And then they go on about the PS2 capabilities

I'm sure you'll find this info usefull, good luck solving the Namco hardware puzzle ;)