I decided to have a crack at it last night...
End result (after a few hours) was I got it working and it is quite impressive. Needed a few subtle code tweaks and a bit of database searching to work out what parameters needed to be added and what to be set to.
I currently only have a dual crystal switch hooked up to two dummy lights but even the wife thought it was impressive when I turned them on and dimmed them via the Nokia 770 orbiter
The first time I have used a GSD device (and ruby for that matter) as other devices I have developed myself have been C++, but it seems pretty straightforward and works well for this device.
Dan, I would like to publically thank you for your work here. I think that PLC-BUS is currently the most cost effective lighting solution in Australia and you have helped make this happen in linuxMCE.
So the plan now is to update the wiki with a similar install guide to the Insteon one. It would be good if Slampt, Dan and Hari could look over this and add/correct any omissions, hope to get this done over the weekend.
Slampt, part of the PLC-BUS command set allows switching status feedback on - this may help do what you want.
Do you want an event published when the manual switch is used or just the state changed so that it be queried by a command?