Rules state that it is who you are registered with, and as Mainland aren't a club (despite being nominated for most fairest club?!?!?), then technically they are still Nomads players (poolmister may be able to confirm). You are also allowed 3 guest players.
2011 Tsunami tournament Rules:
Eligibility
Players are only eligible for the club they PLAYED the 2011 season with unless their club is not participating or they have written permission from their club to represent another club as a guest player