BakaBT WIKI says

How do I get invited?

Right now, the only way to get invited is by passing an interview administered by site staff. These interviews are conducted on IRC, so follow our guide to find your way there.
The Invite channel is #bakabt-invites . Type /join #bakabt-invites to join
Once in the channel type !queue , other commands are !queueStatus and !help
Wait until you are invited to an interview channel. If necessary type /join #channel (e.g. #bakabt-invite-259)
Pass the interview.