Hi Nick,
One of the benefits of running a command system, such as DCS, is that it really isn't necessary to cut the power to sidings. The engine won't start and idle until you address it with the remote.
The only reason to make a siding that has power switched is to turn the lights of passenger cars and such off, saving bulb life. It also will reduce the hours/maintenance counter on the engine.
The negative to doing this with DCS is that you may not be able to address the engine when you switch power to the siding. This is unique to DCS.
I think a viable workaround would be to shut down power to the layout and the TIU. Then, switch the siding on, power up the layout and TIU, change trains and then cut the power to the siding.
A couple of guys have created a method to get the "watchdog signal" from the TIU on layout power up to unpowered sidings. If you want to go that way, post your siding question in the DCS forum or search the DCS Forum for keeping watchdog signal.
