Congrats!
I can tell you a little about how mine went. We were randomly assigned into a group of 3. There were 3 interviewers in the room with us (PT from the community, a faculty member, and a 3rd year student). First they had us introduce ourselves and just tell them a little bit about why we wanted to be a PT.
Next, they gave us a group assignment. A piece of paper was given to us describing the program's current form of fundraising. We had to discuss amongst ourselves whether we thought this was a good idea, and if not, what some other fundraising options we could present as potential ideas for the future. We were given 15 minutes to discuss (the 3 interviewers pretended to chat amongst themselves, but really, one was always watching and seeing how we interacted with each other) and 10 minutes to present our thoughts and ideas.
After that, each interviewer took a turn dishing out questions. From my pre-interview prep with mentors and previous students, I was told that it's good to jump in and be the first to answer at least some of the time. Don't just let the others take control. It was frustrating sometimes when someone would say exactly what you were planning to...so you've gotta think on your feet and come up with something original, but still meaningful to you.
Overall, they just want to see how you interact in a group setting in addition to the quality of your answers. Good luck!
