So, this doesn't take place after flynn ot TJ's routes from echo. That leaves Jenna, Leo and Carl's routes.
Actually, I believe one of the authors said that Arches doesn’t follow any of the character’s routes from Echo, as it is a standalone sequel.
What we do know is that something did happen back in 2015, but this game might not be following any of the Echo cast’s routes. Hell, who knows if any of the characters from Echo will even make an appearance.