Don't bother with Holland and Rubicon. Several other users have written reviews of him before me so I won't bother, but no classicist holds his views or work in very high regard, and historians also like to point out that he's not a historian by training and has no background in classics whatsoever. Rubicon is a book about George Bush that made a splash because it came out in the wake of 9/11 and the beginning of the Second Gulf War, not because it's an even halfway decent piece of scholarship--one hesitates to even call it scholarship, as Holland advances no theories of his own that he supports at all (or supports logically, since his command of the original textual material is tenuous at best) and only regurgitates the work of others, which is almost always frightfully out-of-date--Holland relies heavily on Victorian scholars like Mommsen, whose work has been thoroughly sidelined since at least the 1930s. I suggest you pick up a copy of Gelzer's wonderful biography of Caesar, or if you really would rather prefer something written specifically for a popular audience at least go to Goldsworthy (whose work I also have serious problems with, but at least it's better than Holland).

Anyway, I don't really know why Holland would claim that Caesar only "had plans" of rebuilding Carthage and Corinth as late as 45, when he refounded Carthage and began the process of its rebuilding in 49. Perhaps Holland has mistaken Caesar's plans for Carthage with those of Corinth, which he did not refound and dedicate until 44 just before his assassination and which was not completely rebuilt for nearly a decade. Or perhaps he has mistaken the date of the completion of the Caesarian colony in Carthage in 44 for its initiation--mind you, we only date that as the end of Carthage's resettlement because that's when the Caesarian colony stops being settled by Caesarians, since Caesar was dead. Carthage continued to be settled throughout the 1st Century, B.C. and was quite large by Augustus' death--it's just that it was no longer a Caesarian colony. Keep in mind that neither Corinth nor Carthage were totally wiped out and devoid of life--settlement continued in both cities after their destruction in 146, although it was rather minor (at least in the case of Corinth). When Marius fled their he wasn't in some deserted wasteland, but in a settlement that, although depressed and a shadow of its previous self, was capable of sustaining him and his ambition. But neither settlement was recognized as a city by the Roman state, and neither settlement was a Roman colony. Nor was Caesar the first to attempt a refounding of Carthage at least. During Gaius Gracchus' tribunate in 122 he attempted to found a colony at Carthage in support of his distribution of public land distributions, but the motion was dismantled a little later by Gracchus' enemies, despite some headway having been made