Guys, it's The Judas Contract, firstly. (the name is a reference to a pretty famous betrayal story.)
To answer the question though. I think it really depends on a few things, and these are questions i'm now super interested to find out:
1) Was Evelyn working with Prometheus before being on team Arrow?
If so then the train fight was entirely staged. That being said, if he was working with Evelyn already, maybe he figured it would be an easy win.
2) Was she recruited? Possibly after the big "you were a murderer" reveal?
If she was a plant on the team, it could be considered a loose adaptation (very loose). Even though it's Prometheus instead of Slade, and Evelyn instead of Terra, and Team Arrow instead of the Titans, and superpowers aren't involved...
I think it's more likely it's just the standard "mole on the team" trope.