I think the side missions are generated randomly. I mean it would be mega boring once you knew where EVERY side mission area is.
Some sides missions will be always the same, which makes sense. Blowing up a second doorway can't be generated randomly. Other side-missions depend on your team status: Changing class, healing/reviving/buffing someone, give someone ammo, repair turret, take command post x, ... Others will depend on the other team: Hack turret x, interrogate player y, defuse landmine, ... Even if most objectives are the same, you'll always have another battlefield to play on depending on a lot of factors.