Armagetron Advanced works on the Macintosh LAN at my school, but a demo version of BLOCKLAND paired with a retail version does not.
The game shows up in the Lan query, but when I attempt to connect it tells me that the game does not appear to be a lan game. I even changed the port on the retail host to 4533 or 4534 which are the ports that Armagetron Advanced uses, I then did a manual ip connect and it still told me that the game did not appear to be a lan game.
Tremulous for mac also works like a dream on the network, however, I did not try the ports that it uses. After much experimentation, I just gave up.