I forget the exact terms at the moment, but there are (I think) "Xing plates" that you can use that contain no signage at all, to provide the crossing itself (attach it to the road and the slaves, not the track itself) and then look at the wide variety of "NRC" (No Road Connection) assets that you also attach to the slaves (with invisible track or "red wire" - there's a number of light-only assets here, including some DIY posts and floating lights.
As well, with a little effort and careful placement, you can use nearly any existing crossing object with ATLS, just connect them to the road and your slaves, line them up with your existing track (without connecting to the track) and go. You may have to play around with some invisible track over the crossing... There used to be a tutorial for this around somewhere, possibly on the ATLS site (mentioned below). The nice thing about the xing plates I mention above is they have no "visible" track so are more customizable as far as how the align with your track.
As to the first question, I'm not sure what the status of ATLS in TANE is, I thought it worked but I've yet to test it myself. I would strongly recommend looking at Boat's site (google Boat ATLS) for the instructions, you may find you need a "corrector" placed if your session begins with a train within the detection zone.
