I can't help you with CBus but some more food for thought for you, having just 90% completed a rewire and built in intelligent control of the lights.
After much deliberation, and like ericmark I was also worried about future maintainability, I came up with the following system for lighting control.
2 standard steel enclosures housing a DIN rail each have been used. 1 for the downstairs lights mounted under the stairs tight up to the ceiling, and 1 for the upstairs lights mounted on the loft floor. In both enclosures a single rail on the long side of the box terminates a 2 core & E from every lamp and 3 core & E from every light switch, plus the radial from the CU and also an extra 4mm earth ( i like redundancy in a system and as I intend to use C6s for the lights it will drop the loop impedance even further).
All the connections are standard DIN rail terminals. The earths as usual go straight to the rail, the neutrals are bussed together across the top of the terminals, leaving only the switched lives to deal with on the other side of the terminals. In this way 2/3 of the interconnections are done with no further wiring.
The mains wiring and low voltage control wires do not share ducts. And the box downstairs has intumescent to shut the wiring duct in case of a fire.
The system has the following important (well to me anyway) features.
1) As the DIN rail is tight to one side this leaves most of the enclosure free for control gear. Also isolation and clearances are easier to achieve - all the mains stuff is one side leaving bought-in kit or custom PCB to do the rest.
2) There is no intelligence or other componentry to go wrong in inaccessible places. There are no joints in the system other than the ones in the enclosures and at the fittings. Inspection, test and trouble shooting is a doodle.
3) The system can easily be setup to work in exactly the same way as a traditional system by installing some temporary links into the DIN terminals, leaving you free to decide what control gear you want to use and when.
4) Every switch has a 3 core & earth to it just like you would with a 2 way switch. Some lights in the building need this, but with relay control if/when the control system fails it can easily be put back to traditional operation by removing the control system power. Also the system looks and behaves like a completely standard install should you so choose.
5) Each box has a couple of generic control wires to it allowing pretty much any control gear to be fitted. One is CAT5 the other is 2 shielded twisted pairs to look after anything that is RS485 like, so MODBUS/ProfiBus etc etc. This will give enough suitable wiring for balanced data comms and power/isolated power.
6) light fittings are easy to install as there's no overcrowding of terminals. Plus the system can be partially installed and run, adding to it as and when.
7) the core connectors of the system are industry standard and won't disappear, the control gear could be easily changed or scrapped completely.
8 ) The DIN rail terminals also obviate the so called 'choc bloc' connectors and/or joint boxes replacing them with cage clamp terminals which I've always prefered.
9) The CU end is normal, with 2 radials going out.
10) adding additional light fittings or functionality is very easy. So it would be reasonably future proof. Dare I say that!
Okay the control gear is different from what you'd usually find domestically but the rest isn't far away from regular stuff and could be maintained by a competent electrician. But stick a SCADA system in there and you're into industrial control and with its associated higher cost.
There's some lovely touchscreen HMI stuff about now but it's not cheap.
