Using xbmc-send one can remotely via SSH trigger a rescan of the media library. For example the videos like here below.
apathy:~ $ xbmc-send --action="XBMC.updatelibrary(video)"
Sending action: XBMC.updatelibrary(video)
The xbmc-send command can be used for a lot of things and is well worth looking further into.
This works fine for me on OpenELEC version 3.0.6.