It occurs to me that I've already explored magic-based construction methods, when I had a circle of mages repair the Øresund Bridge in a fic. Silly me, I forgot.
Didn't need any observers from OSH/OCC/MBIE for that one, either, although it did let through the first responders - the insurance agents! (gasp horror)
Anyway, there don't seem to be a lot of work crews going out in Finland, full stop - their reclamation efforts are paltry compared to the Swedes, who don't use mages. Norway might have an Icelandic-style mage on their work crews, but only to apply protective runes - otherwise they'd be asleep on the job!
I'm not sure anyone would automatically use magic for construction inside of a cleansed/safe area.