Hi there and thank you for your question,
I will try to assist you with your legal question but please feel free to ask as many follow up questions as you like until you are 100% satisfied.
Yes, unfortuantely they are.
There are no laws or regulations that (i) specifically require the municipality to place warning signs about up-coming speed cameras; and nor are there laws or regulations that (ii) require the speed cameras to be clearly visible to the motorist.
That means that the municipality can paint them whatever colour they want, and can "hide" the cameras in grey utility boxes, or wheelie bins, or in the bush, or wherever they want.
There are many many articles online dealing with this topic if you want to read up further.
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Good luck and best regards,