I have layouts for a number of Byz cities ... they are in the book, uh, The Oxford History of Byzantium, the plans there are for a number of cities, though I have a sneaking suspicion that by the beginning of M2 a number would be in other nation's hands.

Although, the book does give a good overview of the basic layout of a generic town, so it might be useful, if CA actually gives us easier-to-edit city layouts.