I heard there are only 8.000 user slots available in that tracker site and all are full...
One thing is for sure: nobody will give an invite there without getting something in return
1. Anyway i see some sell their accounts:
Selling TranceTraffic Donor Torrent Account
2. Ask someone that has an account there
I see they have a Steam Group
Steam Community :: Group :: TranceTraffic
3. You could also go to their iRC channel and beg or bribe them (or both):
server: irc.p2p-network.net
channel: #trancetraffic
EDIT: Unfortunately their irc channel works only for registered tracker site users