I've tested with the list on the transmission-qt main window on linux with orca 3.13 pre.
0) make sure both orca and transmission-qt are running.
1) Add at least two torrents so there is something to select.
2) repeatedly press the tab key to focus an item in the list.
3) Press ctrl+a to select all the items in the list.
4) Press and hold down the ctrl key.
5) While the ctrl key is held pressed down use up and down arrow to move in the list.
6) Now press the space bar to deselect currently highlighted item.
Result: thereis no audible event informing user that the selection has been changed. When comparing the behaviour with gtk lists and tables orca should say not selected in this situation.