No, it existed. It was midways attempt to make MK a "tourny" game. They only tested it in a few locations, and there are few if any boards left out there. I'd like to find a board set, not only to run in my cab, but I'd send it somewhere to get it dumped for MAME lol.
and I believe if it was dumped it would be nearly worthless in MAME.
The impression I get from every piece of information I've seen about it is that there was some kind of client->server model (rather than cab->cab connections) The server software would manage the games, perform the matchmaking, handle the rankings etc. etc.
Without BOTH the server and client software, it's not going to do much, and you can bet there was only one copy of the server software somewhere at Midway and that's long gone, even if the boards aren't.
So, even if a board shows up, it probably won't be that interesting from the point of view of a gamer, I'm still inclined to think a lot of what is said about it is nothing more than rumours tho, I'd be surprised if there were extra characters, rather than just a crude attempt to implement a network ranking system which ultimately failed.