Many years back the city released a report on rebuilding Dorchester Avenue. The expensive, pretty useless project (I live just off Dot Ave) actually states that since there are six different types of lighting used on the many miles of the street, all should be ripped out and replaced. Even the newer acorn lighting installed within the past ten years in some areas.
Our government is rich, brimming with extra money to throw at anything, so this is a pretty good use of all that spare cash they have laying around.
Additionally, just due to the fact that the regularly-scheduled timing of this wasteful project happens to fall within the hazy window of the failed, so-called "Stimulus Bill" this project has been branded as part of that failure. Even though it would have happened anyway.
Does that answer your question? You just can't have light poles in Andrew Square that look different than light poles in Lower Mills. Duh.