From what I can tell scenes are setup directly through LinuxMCE. It takes the place of the insteon software. So scenes will be defined within the web interface of LinuxMCE.
I'm more familiar with using Insteon via Misterhouse, as that's my present production environment. With Insteon, you can have on device scenes, where multiple devices are linked and the scene is executed with one command that is acted on by all devices simultaneously. There were past comments on the LMCE forums that scenes for Insteon devices were simply LMCE sending individual commands to each device, which puts more traffic on the Insteon network in the case of complex scenes. So, my inquiry was more along the lines of "is that still the case?" I had seen comments about someone writing a C device driver, but nothing appeared in the forums or trac to that extent.
Having scene support in LMCE where the scenes are downloaded to the devices and then executed by a single command would ensure a faster response time, less traffic for the Insteon network, and would give a fail-safe capability in the case that the LMCE core was down, so that lighting works the same with or without automation (major WAF sticking point).
Not sure if you're aware of this little Insteon gem or not...http://www.madreporite.com/insteon/commands.htm
Thanks for the reply, and hope that helps!