You can read/download the consultation document in all its glory here. You'll see though that the proposal currently holds that the 60mph limit runs from 7am to 7pm seven days a week, though "further assessment work is being undertaken to refine the operational regime". This could result in the limit only being in operation during 'peak hours', only from Monday to Friday or over a shorter stretch of motorway.
Given that the main inspiration for lowering the limit from 70 is to improve air quality it doesn't take a genius to realise it's aimed at car drivers, not HGVs which can't even (officially) hit 60mph anyway. The same HGVs that AA president Edmund King claimed on Radio 4's PM programme put out 11 times the NOX levels and 30 times the particulates of cars and now lumbering closer to the local population thanks to the new motorway configuration. The HA proposal does offer the possibility of the 60mph limit being removed if air quality improves, noting the impact of incoming Euro6 regulations and the fact that "older, more polluting vehicles will become obsolete and thereby removed from the roads." But before you get too excited you'll see it adds "for the purposes of this consultation, it should be assumed that the speed limit will need to be in place for several years."
918 Spyder owners to drive at the 93.75mph possible in electric only mode, until such point as the battery runs dry and the V8 kicks in. Which, sadly, it will do about halfway through the 31-mile stretch the new limit would apply to.
These and other helpful suggestions can be made to the Highways Agency, which has invited comments from interested parties - including individuals - until Monday March 3. See the consultation document for details of how to get your points across.
You won't be surprised to hear PHers are already talking about this - join the conversation here.