The road network would be repaired - the German army did not keep tens of thousands of engineers on staff for decoration.
Like they did in Eastern Libya?
That sounds rather low. At 300 miles, a truck-based logistic net generally consume more then half of what they are transporting. So at 480 miles we are looking at something like 60% given the terrible infrastructure net. So 240,000 tons make it as far as Tripoli. Then they have to make it out to Benghazi, which is 600 miles. And then they have to travel 300 miles to the front line assuming the front is equidistant between Benghazi and Alexandria.The distance by road (about 480 miles), and that simply defines the amount of supply landed in Tunisia that is consumed in the move to Tripoli. A rough and ready figure might be 25%.
It is an additional 300 miles to Alexandria.
http://www.almc.army.mil/alog/issues/JanFeb01/MS610.htm
Once disembarked, supplies had to be moved vast distances over an extremely limited road and rail network to reach the forward depots. Van Creveld notes that "the enormous distances . . . were all out of proportion to anything the Wehrmacht [the German Army] had been asked to deal with in Europe. From Brest-Litovsk, on the German-Soviet demarcation line in Poland, to Moscow it was only some 600 miles. This was approximately equal to the distance from Tripoli to Benghazi, but only half that from Tripoli to Alexandria [Egypt]."
Compounding the problem was the lack of adequate roads. There was only one "main supply route," the Via Balbia, which stretched endlessly along the coast, often was interrupted by floods, and was laughably susceptible to both air and ground interdiction. Apart from this, there were only desert tracks, the use of which greatly increased wear and tear on vehicles.
If anything, the rail network was even sparser than the road network. German Major General Alfred Toppe laconically concluded, "There was no continuous railroad in Libya. The two railroads, each about thirty kilometers in length, in Tripolitania [northwest Libya] and in the Cyrenaica, were of no military importance." These local factors had a critical impact on German logistics efforts.