Have you tried searching for bus in Forumosa.com’s search function? That’s generally the best place to start when searching for anything. 
Select search topic titles only, and return topics only, and you’ll see a list of existing threads on the topic, some of which have links to websites or pdf files, like this one for instance:
[Taipei Bus Lines - Useful Link
Here is one of the sites linked to:
taipeibus.taipei.gov.tw/index_e.htm
I hope that helps! 