Found the following on a Warhammer 40k site. It is a response from Sega in regards to their takeover of the Space Marine content and the loss of the DLC servers:
Vincent - SEGA, Apr 16 12:01 (BST): Dear Customer, Unfortunately, we currently do not have access to the tools required to sort this issue out for you. We are currently working closely with Relic to get these tools in place as quickly as possible. We will let you know as soon as we have the ability to assist you. We apologise for any inconvenience during this transition and greatly appreciate your patience. Kind Regards, SEGA Support
However this was months ago, so I'm guessing those servers aren't coming back online. That's a shame because Dreadnought Assault was the most fun I've had on the multiplayer, and now I can't get the Chaos cheevos.