Greetings!
I am trying this out with "Last Train" map and I see it only spawning underground... is there a way to add it above ground instead of or as well??

When you say "it", are you referring to conductors, or workcarts themselves?

If you are not seeing workcarts spawning above ground, then you probably need to install the Workcart Spawner plugin, or follow whatever guidance that map comes with.

If you have already figured out how to make workcarts spawn above ground, but you are not seeing any conductors, this is because the plugin isn't currently smart enough to know where to add the triggers above ground, since above ground tracks are implemented by mappers, rather than following predetermined rules and such. This means that you have to add the triggers above ground yourself. This process is documented in the plugin documentation.

In the future, it is probably possible to have the plugin automatically detect certain prefabs to automatically add triggers above ground, the same way that the Workcart Spawner plugin works. Does that seem like something you would expect the plugin to do? The main problem with this automation like this, is that there's no way for the plugin to know that its safe to do this. Below ground, the tracks follow a certain predictable system, such that always turning left avoids all collisions. However. Mappers may have not designed above ground tracks that way, meaning workcarts could end up in head on collisions, or pile up on dead ends, ultimately leading to server crashes, as some early beta testers have experienced. Because of this risk, the above ground trigger setup is an entirely manual process. However, I'm open ideas on how we can make it more automated in a safe way if possible.

Once you have figured out a set of triggers that work well for that map, I suggest sending those to the map maker so that they can bundle the json file with their map release, so that other customers can benefit from having above ground triggers already set up for them. There are instructions in the plugin documentation on how to do this.