I don't think it's really a case of whether LAT offices can cope, as Clash points out the afternoon deliveries will be resourced to the traffic they receive whether it's 200 or 7000.
The size and quantity of Tracked that move on to afternoon deliveries will depend on which is the better financial outcome for the business, separating the smaller stuff and sending them through the Mail centre network for morning delivery or keeping them in the superhub system and sending them directly to the delivery offices for afternoon delivery.
Since the superhubs will come online in stages I think it will probably be a dog's dinner combination of both to start with but it's hard to see a justification for the smaller tracked to be done by van in the afternoon after a walking postie has covered the ground already.
The last thing you want to do with parcel deliveries is have them basically walking the length of every street hitting every third door with something that goes through a letterbox. It's supposed to be about saving money after all.