I'm pretty sure addresses come from the MassGIS batch import in 2009-2013. You can read more about that here.
https://wiki.openstreetmap.org/wiki/Import/Catalogue/MassGIS_Addresses

Since there's >95% local coverage I just add corrections with the local convention of semi-colons. Not sure why the importers departed from convention: could have happened prior to setting the convention.
