OK, lets see
so you fancy a multilevel table
well, the houses You have you can use without fixing - would be pointless to fix haouses anyway
so:
lowest level: channel flowing through the table
1st level - underground train station
street level - some train station on top of the underground, with the stairway from beneath opening to the hall of the train station
the underground levels should be open to the sides, so you can game them
the underground line should run along the long side
the channel cutting the table in two
make secret accesses from the underground tunnel to the channle water level, along the short sides (open)
on the long side opposite the underground station you make the central sewage, big enough to put strange vehicles or boats in it
now the train station is on one side of the table, connected with the underground station
make the side of the Hall to be opened to the Hall
the streel level entrance is slightly ascending to the Hall level
from Hall level there is a stairway to the Train Platforms
so the train track crosses the channel over a trunnion bridge and continues on the other side on a viaduct (since You have gained height through the raising of the station hall floor), the street runnig between channel and train station and passing under the trunnion bridge should be accessible for traffic
don't forget to make a short traffic bridge on street level to get cars and people on the other side of the channel
you get a table with 4 main levels and interlevels, to be used with boats, trains and cars
if You still have space, you can add some of your buildings in predesigned spaces between the streets
playable all around and on top
urban enough?