I was kinda in the same position as you over the year ago, but I was already a partner and wanted to transfer store because of uni. I still had to do a group assessment, however the applicants were all external. Unless it a group assessment for current temps looking for a permanent position, expect nearly exactly the same exercises as your first assessment.
When I was a xmas temp, the managers would look at the budget, decide how many temps they could afford to make permanent (if any), and choose the best performing temps based on a points criteria. So for example, When did you start?, How many sickness/lateness have you had? What's your customer service like? How do well do you get on with other partners?, all are taken into consideration, or so I was told by my section manager at the time.
Then again I haven't been "formally" with the partnership in over a year now, and I know they have changed certain protocols, and assessing temps maybe one of them.