Correct, they are not covered under any plan. You will get a side with your entree (and the potato gratin that comes with the NY Strip is VERY good ), but to purchase the extra sides (which typically can serve between 2 and 4 if I overheard Eduardo correct on Friday) you will be paying extra. The same goes for the other TS restaurants that have specific "Side Orders" menus as well.
In case there is something in particular you want, when I was there a few weeks ago we were able to substitute any side for the one listed with the entree.