It connects to Fasttrack but pools it's own users. Kind of confusing really.
It sounds a little like what Bearshare does. It connects to it's own first then other gnutella clients.
"There's been much speculation regarding iMesh's participation in the FastTrack network. To immediately clear things up, iMesh does connect to the FastTrack network. The user count one reads, typically over 1.2 million, is the amount of iMesh clients currently connected to the network. While being its own independent pool of users, the network of iMesh users also communicates with KaZaA and Grokster clients. "