To watch live TV in XBMC using your HDHomeRun you need to configure your channels. You will need to create a text file containing a URI to each HDHomeRun channel. Here is an example URI: hdhomerun://1019DD95-1/tuner1?channel=8vsb:50&program=1. You then add a Video source in XBMC by pointing to the directory containing the text files you created.
Below is a graphic on composing the URI. The screenshot is of the HDHomeRun configuration tool on my Ubuntu system.
I put my files in a directory called "Live TV" in my Videos directory. Here is a screen shot of those files:
Below is a screenshot of what the channel line up looks like in XBMC.
Below is a video of live channel viewing in XBMC.
Below is a video of live channel viewing in XBMC on an Android Nexus 7 tablet