TMCC signal and toggle switches

That shouldn't pose a problem. However, before doing that, I would try it without isolating the common. You may not have an issue.

Should be no problem. Toggles for yard tracks is very common, no pun intended. I use toggles for the yard tracks and it saves the conventional from starting out too fast from the yards.

Ralph

I wouldn't think it would be a problem as long as you had a good connection from the outer rail to the U terminal on the base.  You could run into a problem if you bundle the hot and the outer rail runs together for any distance.  This can set up a capacitance in the TMCC return (outer rail) and block the signal. 

I don't know what you mean by this though "and a loco on that track would hopefully avoid the operational problems a ground plane could normally solve".  The "ground plane" corrects a signal problem.  Something is blocking the air (ground) signal from reaching the engine.  The ground wire acts as an auxiliary antenna for the TMCC signal.  Why do you think an engine on the track would help?

Not criticizing, just curious as to what your thinking is.

Thanks for the replies.  Chris, I just didn't say what I meant very well.  I was just wondering if isolating all three rails in several dead end sidings and only powering up the hot and commons thru a toggle when an engine would be on one of them would be a way to eliminate the chance of mixed signal issues that can occur on close parallel tracks; the kind of thing that a ground plane would usually eliminate.

Bucky