I believe taht most people who doesn't use the car to go anywhere (I do), use underground, thus being bus transportation secondary. I don't know the bus lines vey well. I couldn't tell.

I believe there is no map of bus lines, although there used to be.

I just found this in the net, which is a relation of all the lines and itineraries, but I think it won't help you much. Anyway everybody goes by metro, it's cheap, faster and safe.