The bridge structure has not actually changed, it was jacked up. All that has been added are the additional concrete filled steel cill beams painted "sapphire blue" and some additional brickwork outboard of those beams to fill the gap. The stairs to the Down platform have also had three steps added.
The mystery brick tower is an access chamber for a sluice valve where two sewer pipes join after crossing the tracks at roughly 45 degrees. In the photos you can see the long timbers under the rails to bridge over the pipes. I presume the tower is that tall to ensure that when the sewer pipes are surcharged the water will not over flow out of the chamber.
Some good news - in a massive middle finger to my earlier posts hypothesising that there wouldn't be much if any electric freight over the GOBLIN, the very first train to use it in anger (and not for testing) was a DB Cargo freight train from Dagenham to Mossend.
Just been having a dig around for GOBLIN related issues. Found a couple of recent Line User Group documents - note these also span into rolling stock issues but I don't propose to post to two threads.
First document is a summary of some of the recent success, failures and future hopes for the service. This is a presentation to the London Assembly Transport Cttee who currently have an investigation into London's rail services. Also includes a set of recent Mayor's Questions which were all posed in this month's Mayor's Question Time. It also sets out some ideas about how to try to improve the current problems with GOBLIN service reliability - includes ideas I've not come across before.