I believe it should be a RAT - so you should get a few notifications - one that it was revised, that you were removed from it and then that you were added back to it. You can then drop it if you desire and go into SUB with all the standard protection rules. If the trip changes more than 4 hours (I believe) on either end then it should be a RAT. If you take it, you get the 125%, etc. etc. Look up the RAT part in the CBA or give Crew Scheds a call.