I believe part of Marias Pass is a DLS route, because it was built in to at least TRS 2006. But there are longer versions I don't think are on DLS, and need to be purchased through the HP-Trainz website.
Marias Pass Route Plus, Marias Pass Route X, and Marias Pass Route X45 are full versions and they are paywayre. Marias Pass route Approach is on the DLS and is a demo version of the full versions.