There's a more up-to-date plan over at the Steam discussions forum (no account required for reading). The locos will be 03 and/or 08 and/or 37 with Mk1 coaches and/or freight wagons but I'm going to release two editor updates before that. Developing the editors is taking a lot longer than I originally expected because they're technically quite complex. I shouldn't really give any dates because I've done such a poor job of estimating them in the past, but the next update is quite likely to be released next month.