Does speed sign on back of truck change speed limit of overhead cameras?

[Craig-M80]

I was travelling greensborough bound on M80 today. On the ramp to M80 from Princess Fwy, there was a truck with 40 sign at back of it.
I drove 40 for next 100 metres but everyone else was just going 100. So I increased by speed too. As I passed the overhead cameras, may be I was at 75-80.
Would the fixed cameras have speed detection reduced to 40 to match the speed sign that was at the back of the truck?

 

[Ponala]

The speed signs on the side of the road or the overhead variable signs are the speed limit, not what is on the back of the truck.