They aren't independent, the city will tend to build up along the transit lines due to the easy access to transit. E.g., the NYC outer boroughs and the DC metro area.
Bus lines instead tend to follow where the traffic wants to go. Around here, many shopping malls double as bus stations because the primary aim of transit seems to be circulating consumers around places they will spend money.
This is circular reasoning though. Bus lines go to the mall, but malls are built where the bus lines go. Malls use a lot of space, so carving out a little bit for transit is easy.