Having wrecked a few chains over the years that bit into hidden entombed concrete (plus occaisionally rebar), I question whether the arborist/brick masons of yesteryear appreciably shortened the natural lifespan of any urban tree, Alex Shigo nothwithstanding.
Ditto for trees that were deadwooded/pruned decades ago by climbers wearing spurs. Exception being oak wilt, maybe, but that seems to be a more recent issue.
I think urban trees have far greater and significant hurdles to overcome than being spiked or mortared. Foreign invasive species, soil compaction, turfgrass competition, improper planting/species selection, etc are probably every bit as bad or worse than a cavity getting some ready-mix. And no, I'm not advocating doing same, nor excusing the OP for missing the tree ed 101 class.
Anybody here remember reading an excellent controversial article published in TCI magazine a few years ago by Cass Turnbull (sp?) from Plant Amnesty?
Article was about drop crotch pruning, and how it really doesn't acomplish any significant good at all.