You can figure out how good a view the witness got by googling the streetscape and asking the witness where exactly they were standing and what exactly made them look at that particular house.
So you want a call handler to pop onto google street view in the middle of the call, look at a potentially years out of date street view of the area, and try and guide the caller around, in order to ascertain certain things? That is just deluded and unworkable.
Long and short of it is, don't have imitation, or real firearms visible at any level, either glancing or full on, from outside of your house, at any time, it's not that difficult. They obviously did, because a member of the public was able to see it enough to determine it was a firearm, and the police found it.
Doesn't matter if it's legal to have in your own home or not, it's irresponsible. I've already said I don't do it and close my blinds whenever I know I'll have mine out in an area of my house that is even remotely visible by members of the public or my neighbours.