Please everyone remember that Host WAN is NOT also INSIDE Host. That means, the guards' devices can be slaved to a host but not be in the host. In the BK bank heist example, the Maglock is slaved to the Host's WAN but is not actually an icon inside the host (if you traveled there).
But it certainly could be. Not that it's all that relevant to the question. Well, not really relevant to the question I meant to ask. Sorry, my using WAN was unnecessary and needlessly complicated the matter.
The real question is whether icons that are within a host (devices, files, personas, whatever) are visible to someone who is not in the host. From implications in the book, you can't see an icon if it is inside a host unless you also enter that host. So if a guard's pistol icon was hanging out in his employer's host (whether or not it's slaved to the host in a WAN), you definitely wouldn't be able to spot it if it was physically further than 100 meters away from you since you can't spot things inside of a host. What I don't know is whether the 100-meter signal range supercedes that quality.