Notam question

[Ozfergie]

Others of you have probably noticed the increase in aerial survey aircraft over the Sydney basin since lockdown.

 

It appears they are chiefly Oberon Aviation (power grid ?) and NSW Rural Fire Service.

 

They typically are c. 2,200 ft and have often been operating in popular corridors making multiple passes over a compact area.

 

I have checked several times and am yet to see one Notam - so my question is what warrants the obligation

to seek and have a Notam issued?