I've only played and completed Railroad Bridge and i can say that the design is very similar and well done but the objectives are totally different. And different should not be bad by definition but it's just too easy. I played it alone on hard with everything turned off that can be turned off(drone, crosscom, markers, classes) and it took me 3 times before i got the 'kickin it old school' and 'Railroad Bridge co-op Perfect' achievements. There is no need for a team, just Rambo your way through is good enough. Don't worry about the two snipers on the bridge because general Martin will warn you in his little video feed. Even right after you killed them. General Martin is a very well informed little ###### but he's also little slow sometimes. Just after i killed the informant General Martin notified me about his presence in the area.
Also, enemies will spawn here and there, unlike the original missions where all the enemies were pre-placed. E.g. when i was looking at the base on the other side, while i was standing on the bridge, it was empty but as soon as i got closer it was full of enemies. Well, let's not exaggerate things, there were only 10 or 15 of them...
But even with all it's shortcomings it's still a lot better then the on-rail shooter expierence you get from the single player campaign. You can still choose when and wich objective you'll do first, next etc.
In short: the original mission is much better and harder but the GFX are great on the new one.
Still have to see how the other missions are.