FOUND BY DSMxDSM
Step 1 : Go Onto Black ops Try To Connect To Server
Step 2 : Fail Connecting Then Click Join Session On A Friend Or Ask Them To Invite You
Step 3: As Soon As It Says Accepted Whatever Go Onto System Link Start The Game And As THe Game Gets To The End Of Loading it will come up with a black screen then instead of going to system link it will take you online into your friends game

THIS WORKS PERMANENTLY BUT YOU MIGHT HAVE TO DO IT A FEW TIMES

Edit # 1 : Can someone confirm it works aswell whit the server its not avalaible error?
tell me so it can help more people
EDIT # 2 : COnfirmed Sadly not works Whit Server it not avalaible i hope someone can figure out how to bypass the server its not available error

i hope it helps, works for me, on my perma banned account, but i got reseted

Please If works for you help me to get this topic alive, alot people got banned whit the new update so this thread could be usefull for some people

+Rep if you want (Its not Necessary But i would be happy haha )