The problem is many route builders don't include anything in the description or name to say what the session belongs to. If they are kind enough to say what the session belongs to, they rarely say anything on how to run it. There are quite a few exceptions including the guys from Jointed Rail, Phil Skene, Dave Snow, and others, but those guys are fare and few between.
When I have, rarely downloaded a route with an accompanying session, I always setup a free roaming session, and always open up the route for edit to see what it looks like. By doing these two things, I can see what goes where and get an idea where things are so that when it comes time to drive around, I have an idea where stuff is before I start.