The content is made for the most part by the community. Unfortunately what happens is a content creator will decide that looks interesting and create it quite often for themselves then they will share it.
There are 2,400 assets if you look for bus. Coach gives another 2,000. Unfortunately you need to look through them to find what you are after. Look through sterett's assets, SandC also PLL are worth looking through.
Search "london bus" then use the content creator name to search to see if they made anything similar.
