I sent an email to Mrs. Harris, the councilperson who's the public works committee chair looking into this process. asphalt pavement recycling technology has been used by DOT's and municipalities in pennsylvania for nearly 20 years. There are two main types: cold-mix and hot-mix. From the these two types, there are differing methods to reuse the asphalt.
For the method Mrs. Harris and pittsburgh DPW were taking a gander at, it is a hot-mix recycling process that removes the top layer of asphalt. The top layer is call the "wearing course," and is smoother than the lower courses of asphalt. The result of this process will have a smooth finish, but not so smooth that it's slippery in inclement weather.
The issues with using this asphalt recycling method relate to the geometry, the topography and the existing pavement layers of our roads.
Our roads are narrow and the curves are tight. Our roads have sudden and extreme grade changes along straight aways and curves. All of these issues that I've mentioned make even conventional paving difficult. The equipment used for recycling is large and has the turning radius of a flat truck or a bus. The ground clearance on some of the equipment is variable, but at the dimensions of a bus there's difficulty in maintaining a proper milling depth over abrupt grade changes.
Our roads are underlain with old beligian brick pavers, trolley tracks and sometimes unstable earth.
Like I told Mrs. Harris, the cracks we see on our roads are from issues beneath the pavement that this recycling process cannot solve. Poor drainage, failing base and subgrade layers, land creep and landsliding: these can all cause pavement surface cracking alone or in combination.
Oh, and the process is wicked hot. you wouldn't want to be within 500 feet of this process because it requires temperatures greater than conventional paving at longer durations.
In conventional paving, the asphalt arrives onsite around 325°F, and on a hot day could remain above the boiling point of water for an hour or two. However the hot-mix recycling will pre-heat the pavement, mill it, bake it at temperatures in excess of 400°F, then set it back down.