Problem with TGA files with alpha channel?

I created a TGA file with alpha channel in Paint Shop Pro so that it looks like part of a metal fence used on NYCTA elevated stations. In 3DC Pro, I created a 2D plane and used the ‘Double Side’ tool to create two sides. I applied the TGA file to the two-sided object using the ‘Paint Tool’ with ‘Tile to Fit’ Flat Wrap option enabled. I exported the stations to Rail Simulator as usual. In Rail Simulator, I can’t see the fences unless I’m next to them. Any suggestions?