If I progress to the next area via the tram is it possible to return back to this area later on to collect audio diaries and other things like you could in Bioshock 1?
No you can’t. This was by far the most annoying thing about the game in regard to the trophies. You need to make sure you collect everything in an area before you move on. Once you get the train to the next area, that’s it, No going back. Dunno why they did it since there is no reason in most cases why the way back wouldn’t be blocked.
If you are aiming to get the trophies, make sure you get all of the collectables and take care of business in each area before you progress to the next one.