John,
I looked at the option to use Forest Road 74, going below Osier, crossing and parking some place south and hiking in across the Forest but was unsure of the terrain or any clear route. So figured, I know the tracks and Toll Road go to Cascade Trestle, I would just hike in that way. The easiest part was walking across the parking lot at Osier...
My route was not terrible, but also not easy. I'm not in 'great' shape and the lack of abundant 'oxygen' in the air in Colorado did not make it any easier. The Toll Road from the track level down to below the bridge, I think is still much easier than going directly over the side of the embankment. Crossing the river is not 'that bad' either, it's just cold water to adjust to. The key was moving real slow, careful foot placement and using the island to spread the river down some to be less deep. When I tried some 15 years ago or so, slipped, fell in and the water is much colder when sitting in the river.
I think the "other side" presents a great photo angle and is well worth the trip (once?). But much less other key places (Toltec or Mud Tunnel, etc), you have to accept that you are using your day to get maybe the chance to take pictures twice, the one Eastbound train, and the one Westbound train. And as I found, if the light is not right, if the sun and clouds are not perfect, when the train gets there... to bad, try again next year ?
Frolin