Regarding Taz, the word going around is that his contract with World Wrestling Entertainment included a 90 to 120 day no-compete clause, so don't expect to see him officially debut in TNA Wrestling until June or July. Current plans call for the former ECW wrestler to become the mentor of Samoa Joe upon his debut.
Mick Foley and Jonathan Coachman endured similar circumstances when they parted ways with WWE last year as their contracts included a clause to prevent announcers from joining other broadcasting entities straight away — not just rival wrestling organizations.