I don't know about transitional (I applied to mostly prelim medicine positions for my advanced), but I know some of my prelim interview offers included a dinner the night before. I am hoping maybe prelims will understand if I don't make the dinner, however, since scheduling as many advanced interviews as possible is my priority. But your prelims should let you know this info as soon as you schedule an interview with them.
No dinners for any of my prelims - Washington hosp (DC), Drexel (PA), Robert Wood (NJ), Brookdale (NY), St. Peter's (NJ). Same story with transitionals - Tufts (MA), St. Barnabus (NJ), Mamonides (NY), Einstein (PA).