I'm afraid it won't be "whala" (
interesting spelling 
). The reason is, the Trainz world is flat, a plane, as Bob Pearson has already explained in posts #4 and #10.
Geographic coordinates as expressed in latitude/longitude mark a position on a spherical shape instead, the common model of Mother Earth. Now take an orange (our Earth), peel it, and try to flatten the peel. The peel will stretch and tear, and you will get your fingers wet. Obviously, it's not an easy task, not without losses. Surveyors and map makers call such flattening attempts a "projection". There are quite a few of those. And half of TransDEM is about map projections. What the projections all have in common is to try to keep the losses (wet fingers) to a minimum. The losses are called "error". Similar to Trainz, map projections also have a world origin. And the closer you stay to the world origin, the smaller the error.
Now, the map projection in TransDEM is called UTM/WGS84. It's the most common one in the field where we are working here. Like all other map projections, it has a a planar Cartesian coordinate system, and like most others, coordinates are in metres. This makes it rather easy to map UTM coordinates to Trainz World Coordinates (refer to Bob's posts). Simply add an offset and invert a sign, and you are done. But that offset needs a concrete value and that's where the Trainz World Origin comes in. TransDEM "misuses" the WO to define that offset for its own purposes. It should be noted that the WO, as set by TransDEM, will always be slightly off, when interpreting its lat/long coordinates. That's because TransDEM positions the WO exactly at the center of the central baseboard of a route, at Trainz World Coordinates [360,360]. It will then set the geographic coordinates (lat/long) for this. Since the resolution of lat/long in config.txt is quite limited, there will be a rounding error. Nonetheless, TransDEM will be able to figure out the precise value. To summarize, a Trainz route created with TransDEM will always be in UTM projection. With the Trainz WO properly in place (or with the TransDEM info file as a backup), TransDEM will have all the projection parameters, needed for future maintenance.
On the other hand, we have the Trainz' internal lat/long coordinates. We already have learned, these are quite irrelevant to the inner working of Trainz and Surveyor in particular. Lat/long define the solar orbit (In the Trainz world, the sun rotates around the earth), and should affect lighting, but they are not used to locate objects. (Objects are positioned with the metric Trainz World Coordinates, see above.) Again, since the Trainz world is flat, Trainz also needs a map projection to associate a lat/long reading to a given point on a Trainz baseboard. We don't know about that projection. What we can figure out, it does not appear to be UTM/WGS84, but something different. Lat/Long-Reader (and similar tools) read the Trainz lat/long, because that's the only geographic coordinates the tools have access to.
Since we have different projections there will be a discrepancy between Lat/Long-Reader (unknown projection) and UTM as assigned to Trainz World Coordinates, Martin has pointed this out in post #5. There is an old thread in this forum that gives some figures about the magnitude of that discrepancy. For bigger routes and further away from the WO it may matter indeed (independent of the inaccuracy due to rounding for the TransDEM-placed WO itself).
However, a TransDEM-based routed shouldn't have the need to refer to Lat/Long-Reader and its siblings. Built-in functionality in TransDEM with topo maps for ground textures or aerial images on UTM tiles and particularly vector data is intended to give you the means to find exact geo locations in your Trainz route.