It's true that there are a handful of mods for WCIII and StarCraft 2 (such as "Desert Strike" and "Squadron Tower Defense" for SC2) that allow for certain forms of tower defense with simultaneous creep spawning and defending. However, the gameplay dynamic in all of these mods is completely different -- turns are usually simultaneous; there are no dropship pads as part of the mazes (or if there is some equivalent, it's in a separate area, as with Desert Strike, and not part of the maze itself); you spawn each individual creep yourself individually; there is no territory control mechanism, and so on.
There are also many additional aspects of City Conquest, such as the path highlighting arrows, that can't really be done effectively as part of a WC3 or SC2 map, and which are really integral to the gameplay, since they let you know what path enemy units will take.
So the mechanics are radically different, and City Conquest has a completely different dynamic -- one that, to our knowledge, hasn't been explored.
Additionally, regardless of any mods, this particular territory certainly hasn't been explored yet to any appreciable extent on mobile devices. There are a handful of mobile games, such as Anomaly HD, where you play as the creeps instead of defenders ... and a handful of others, such as "Defenders of Ardania," where you play offense and defense at the same time. But both of these are completely different dynamics from the gameplay in City Conquest for all the same reasons listed above.
For example, in "Defenders of Ardania," player positions on the map are fixed; there is no territory control mechanic; players must spawn each creep manually; and so on. So it ends up being a completely different dynamic.