Wire diagram for a 200 snap relay

Not sure this is what you are after, but here's a couple from Atlas showing the #57 switch controller and a #200 snap relay and LED control. There is also a web address in the instructions for more info. Going to go check that one right now myself.

The above mentioned links seemed to be mostly HO. Here's another for manuals and wiring diagrams for Atlas-O stuff that I had saved.

Atlas-O Info

If  you parallel the coils of the M200 Snap Relay with the coils of your Atlas switch, you have a DPDT set of contacts to drive indicators or whatever else you'd like to drive.

200 Snap relay   Appears to have two sets of normally open/ common/ normally closed.  Left top and bottom of this picture.   The three terminals right end of the picture would be common center/straight/ and diverge, similar to the Atlas switch motor.  All momentary power. 

MTH Dwarf  30-11038  It appears the MTH dwarf has it's own relay that can be adapted to Atlas track.  Click on the underlined phrases to link. 

MTH Dwarf wiring diagram

Atlas dwarf lights were designed to hook to the two input terminals of a regular Atlas switch motor via attached PC board. 

Probably not a bad idea Dale, the Snap-Relay doesn't like continuous power.

I've used Atlas snap relays. The problem is that sometimes the plunger will bounce when the coil is pulsed. It's basically a switch machine with relay contacts instead of a throw-bar rod. Functionally, it's a latch with two internal coils. What would have made them better is if they had an over-center spring to lock the contacts in place when thrown. One thing I do like about them is that with the DPDT contact arrangement, you can lock out each coil once thrown so it won't burn out if the switch is held down.

Or you could buy the Atlas dwarf signals that work with the standard Atlas switch motors without the 200 snap relay.  Click on the underlined phrase for the Atlas wiring diagram. 

FWIW - I note that the three latching coil relays offered by automation direct (as referenced by Dale H) are 1) due to be discontinued and 2) according to their FAQ:

Question

Which of your relays are OK for continuous use? (Power to coil maintained indefinitely)

Answer

All of our Solid-state relays and electro-mechanical relays are OK for continuous use. (Power to coil maintained indefinitely) The Latching relays and timer relays are not OK for continuous use.

- Rich

I'll certify that a simple electronic solution will run forever without burning anything.

Something as simple as a set/reset latch like the CD4077 with a diode, resistor, and cap for each input from the switch coils would give you an indication of position.