They are really cracking down on adding extra things to the entree. I know at all of the places we ate, the servers indicated that we could add the lobster or shrimp to the entree, but it would be billed separately.
However, at Le Cellier they had a special the night we were there that included the lobster tail with the entree and that was included on the dining plan. He also said that we could substitute the appetizer for the lobster tail with the entree.
We found most servers to be really helpful in assisting us is maximizing the use of the plan. We even had a couple of people in our group that didn't want to order appetizers or desserts and he brought out sampler trays for them anyway (the more items on the bill, the higher their tips).
Addendum: Ok, I just reread the post... a $28 lobster tail being added to the entree?! I'm not sure I would bank on that one; however, since it is a 2 TS meal, they might do it, I mean they do have that $55 beef and lobster meal that I'm sure you could get. Hrmm... I wonder if you couldn't get the dinner for 2 ($80?) and only use the 2 TS for it. Go for it and then let us know what happens. ;-)