ccamara
Thank you very much, James! It's funny, that example makes the opposite I was considering: he uses building=office (I believe building=public may be more accurate) and amenity=public_building (which the wiki states that is highly  discouraged http://wiki.openstreetmap.org/wiki/Key:amenity and prompts to tag with office=government).

Maybe the correct tagging would be building=office
office=government

but I have my concerns whereas using building=office instead of building=public