There are some great routes and activities on www.train-sim.com in the file library there.
Some other payware websites are
www.3dtrains.com
www.mapleleaftracks.com
www.3dtrainstuff.com
www.dieselswest.com
www.dekosoft.com
www.trainartisan.com
www.digital-rails.com
www.geocities.com/trainsim1
The Atari version in the same as the Microsoft 1.2 (Actually 1.4, they labeled it wrong)update on their website, it's just that Microsoft sold the rights to sell MSTS to Atari.
I'll try to find out how to open the AE, for now, type Train Simulator Editors & Tools in your search.