They can train in any order they choose. If they must they will pay passover, but they will train in the most cost effective way they can. Trying to figure out when you will go to training relative to somebody coming out of the same seat and going to the same seat would be easy. The hard part is when you are coming out of different seats and going to the same seat. Ask the guys who got excessed out of ANC a few years ago. It depends more (I think) on which seat you go to rather than the seat you came out of.
In my opinion they will gladly pay passover for a few months to whoever they have to in order to train folks coming out of the 727 first, in order to avoid the DC-10 situation again. Just my opinion. Trying to guess the training letter fallout is almost impossible with the excess, much easier with a regular vacancy bid.
Good luck to all.
FJ