I have tested with transmission-qt QT 5.3 and orca 3.13 pre.
0) make sure both orca and transmission-qt are running.
1) add at least 1 torrent so there is something to act on.
2) focuss the list.
3) press the applications key to open the context menu.
4) Press down arrow several times until you hear remove.
5) activate remove item by pressing the enter key.
6) Notice the prompt of the dialog is not spoken. Sometimes I can hear it once after pressing the tab key and notice you are unable to hear that prompt again even when trying to use so called flat review to review the screen.
Flat review sometimes works and other times it does not but I am unable to predict when and where.