Could you add linux-uksm-ck in your source?
XBMC shutdown/reboot polkit rules
I undid your modification to the XBMC page, as the polkit rule that enabes poweroff and rebooting when using the systemd service is not present in the current package, as you implied in your modification comment. You can check yourself here. Any reason you thought it was? I added a bug report mentioning this issue here. --Palmaway (talk) 03:31, 9 June 2013 (UTC)
It's not the exact udev rule, but placing the user in the 'power' group, and invoking the shutdown option works for me. This can be reversed by removing the user for the power group, logging out and back in, and invoking the shutdown option again. Now, the box does not go down; xbmc just exits. So functionally, that udev rule is not needed. Graysky (talk) 10:44, 9 June 2013 (UTC)
Unfortunately, this does not work for the systemd service, at least not on some systems. A good idea to post it there. I replyed there and modified a it the XBMC page too.