The legal description is not the usual axles. It is 6 total tyres. From the bylaw quoted in the changeset source:

"No person shall operate a truck or truck tractor, which has more than six tires, along Jubilee Avenue, unless the vehicle is conducting business on Jubilee Avenue or on streets in the vicinity of Jubilee Avenue where Jubilee Avenue is the shortest routing to or from a Truck Route."

Signage at the on-ramps has an indicator for "Yes trucks" with a placard for "Max 6 tires"

I know that nowhere else in the world uses maxtyres, which is why I also tagged it with hgv=no, since that seems like the closest tag that's actually in use that won't get people in trouble with the law.