When it comes to track blocks recommended for running DCS I feel that most of us don't really have large enough layouts to make the issue of duplicate signals (ghosting) a problem. If you follow the recommended block process you most likely won't have any DCS signalling issues. If not, it may work, it may not, and may be more difficult to troubleshoot. There are many people who never bothered creating the blocks and report no issues running DCS.
I am following the recommended bock practice but I use long blocks (some 20-22') so I don't have many. I am a little more concerned about the possibility of a track power lead coming lose and wiring one lead per block would make it very obvious where a problem might be should it occur.
Yes, turning on a siding after the TIU channel is already passing track power will put the MTH engine in conventional mode with 18 vac on the rails. 
I can only image what this looks like and I hope I never find out.
The DCS watchdog signals are only generated for a brief time when track power is applied through a channel. This watchdog signal is what tells the engine that DCS control is present. One work around is to shut down track power on the TIU channel, flip the switch, then turn track power back on.
