Looks like it replaced an older light.

Nope. This has been there since the 80s since it was made in the 1980s.

The pole/arm may have been installed earlier though. If this light was origional to the pole, the arm would have rusted completly.

True. I dunno when this OVZ took over the previous street light, but I'm surprised the pole arm itself is still going strong. Also this pole arm is screwed onto a utility pole, not a concrete or an aluminum pole. Residential areas of Boston have the wooden utility poles. Busy streets have the concrete or aluminum poles.

It's all wood poles here. Except in residential developments made by contractors, which use either post tops or M-250R2s on black poles. Downtown Providence uses MH Acorn post tops though.