Yes it does. This scheme is one of the classic DCC Bad Ideas.

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Unfortunately my DCC colleague Mark hasn't had time to expand on this topic, but I'll touch on a few considerations.

1) The decoder motor outputs and waveforms were never intended for distribution to track. The motor output is a (reversible) pulse width modulated (PWM) signal at (usually) supersonic frequencies.

2) This signal is more likely to cause wide-band radio interference than the standard DCC signal, particularly since the motor (with its inductance) and very noisy commutator is a direct part of this radiative circuit. (When a decoder is used correctly in a locomotive, the decoder circuitry absorbs most of the commutator noise.)

3) The decoder outputs were never designed for this purpose (many metres of wiring with inductance, capacitance, motor suppressions components, transient shorts etc.)

4) Contact of a decoder motor wire with a track wire is one of the most common causes of destruction of a decoder (when a decoder is mis-wired). This event is quite likely to bypass any inbuilt motor output short circuit protection in the decoder and is exactly what will happen if a loco (or metal-wheeled item of rolling stock) crosses the DCC-DC boundaries of your club layout.

Mixed DCC-DC layouts with the possibility of having both active at the same time is generally* a bad idea. This is overlaying another bad idea on top of a bad idea.

Dave

* Some may be aware that my home layout, our clubhouse layout, our travelling exhibition layout and at least one club members layout is wired this way. But in these cases the mixed wiring was done by me. I have had a professional career in designing and building custom electronic circuitry and the layouts so wired have modified DC controllers to enable a correct common connection as well as the two DC wires (only some controllers are suitable), careful attention to overload protection, wiring, testing and the use of extremely fast acting DCC circuit breakers that cut both track wires (most do only one). In the years that we have used the layouts we haven't had a single decoder, booster or DC controller failure due to this scheme. But if you don't have (or have access to someone with) a high level of technical knowledge of DCC, DC and AC circuits to oversee your designs and check all hardware, modifications, etc. you are courting disaster. (The design described by Doug certainly doesn't comply with those constraints).