Presuming the information about the camera's is correct in the magazine article, there is no mention of automatic vehicle type identification.
Some cameras do have ANPR then in theory, if the base computer was quick enough the number plate could be tied to a type of vehicle and if a lower speed limit were applicable the camera system could flag it up and automatically issue a notice of intent to prosecute.
Presently there would be no way for it to automatically identify a domestic car towing a trailer, as it only goes by number plate. Presently it would require a human to review the pictures and to pick out those that are
But never say never, because I have absolute certainty that it won't be long before the systems will be able to automatically recognise when a vehicle is towing and a lower speed limit is applicable,
For your information, There are systems being developed that can measure vehicle axle loads whilst travelling at quite high speeds, These were being trailed for ferry companies to assist with load balancing, but they are also being used in other parts of the world for traffic weight enforcement. I understand the UK government is interested.