Miner Wars 2081
is currently available as an "Alpha" build on the PC with constant updates from the developer/publisher Keen Software House. One of these updates to their test server included the implementation of multi-player deathmatches, of which you can see a teaser right here:
The XBLA version of Miner Wars 2081
is still expected for a Q4 release later this year. While we have yet to come across official confirmation that Deathmatch will be available in the XBLA version, we can only hope.