If memory serves, I think TPB is somehow related to iPredator [1][2], though I'm not sure if that is the case anymore. This may give them _lots_ of experience running VPN software, which would be usable if that is indeed how they're communicating between VPS providers.

[1] https://www.ipredator.se/ [2] http://torrentfreak.com/pirate-bay-announces-ipredator-globa...