Personally, I don't see the issue really.
Using spirits to observe is a commitment of resources. Each wagemage can only have so many spirits, and only be in so many places at once. Also, as a smaller part of the population is Awakened (1%), and a smaller subset AWARE, and an even SMALLER subset actual magicians... Using said magic and rarer resources to keep a look out for mundane activities is a waste unless it's of truly high importance, and rarely do runners enter a high secure area without planning ahead a bit unless they want to fore-go infiltration entirely. If it's that important, the runners should know or have the chance to find out, and plan accordingly.
Astral overwatch of mundane things can be used against security as well. Depending on the instructions the spirit receives there could be:
1) a lot of false reports that the mage has to stop what he's doing and check personally
2) releasing particular animals could cause spirits to appear and attack, causing mundane security to act in a different manner (on alert, "false alarm, the spirit killed a devil rat again", causing a panic if the spirit materialized suddenly, etc)
3) accidental casualties. Did the spirit remember all 20 security workers from the various different shifts? How about regular employees with access? Did the new hire get introduced to the spirit yet?
4) runners could hire other mundanes to break in (gang members, two bit thugs, etc), thereby distracting magical resources
All these make me think that typical astral observation will not really be looking for mundane activity in great detail. They will most likely be looking for magical and astral activity, though they may look for certain important things like the sudden disappearance of an aura mixed with an emotional imprint of pain (killed security officer). But mostly I see it as a case of "Not my department, not my problem."
Astral overwatch of the physical world in detail would likely only be when it's determined to be of great importance, or very temporary such as a deal where one party doesn't trust the other to come alone or whatnot.
On a completely unrelated note but thought I had to share, my firefox spellchecker suggests "garbageman" as a proper spelling replacement for "wagemage". Coincidence?