Google now has over 400 cities included in its transit service. That means each of those organization provides a feed so that the search giant can give accurate routing, schedules and fares. So, why isn't it easier for the average developer to access this data?
There is a list of only 34 public feeds on Google's official transit feed site. That means the vast majority of transit agencies only see the benefit of letting the big guys use their data. That leaves out independent developers, unless their city is one of the 34 (or part of our list of 4 Hip Transit Authorities with APIs).
Very few of the 34 agencies publicly listed even have true APIs. Most have merely provided their data in the zip file format that Google requires. This makes developing a bit more of a chore, as you parse through the various plain text files describing routes, schedules and fares. On the other hand, the format is a de facto standard, so if you figure it out once you should be able to apply it to other agencies easily.
That will come in handy when those other 400 feeds become available. With the direction web services are moving today, it seems unlikely they'll be private for very much longer.