Hi, sorry for the non-topic question, but what is the "alpha texture bug" you people are talking about? and why is it called "alpha"?
The "alpha texture bug" in layman terms is basically an issue with 2D transparent textures causing rendering problems at the edges of the texture, usually trees and other foliage, it's more noticeable at night.
And "Alpha" is the texture channel.
Alpha stands for the transparency channel, which is the fourth channel used besides the red, green and blue ones.
The fringing problem is there mostly because of the engine being unable to properly sort out which parts of the model should be visible or not when they have a transparent texture on it. The bug isn't exclusive to the GTA games (heh, I've seen worse, like in Gangstar West Coast when models that should've been occluded by alpha textures pop out of the scene), and it's more apparent at daytime especially when two transparent textures intersect with each other.
You can fix it with workarounds, as what Dexx tried to do in VC, but a real solution for it would probably be doing additional depth-related operations on the scene, which I don't think that would be easy.
I think, we do not can fix alpha bug, because it is a feature which is peculiar to SA's graphic engine.
By the way, it seems to me that War Drum used their own game engine for iOS-version (in other their games they used own engine), because of this they change the texture format. Also (I could be wrong) they have reduced the size of the game with using aliases for textures - something like shortcuts or links (?) - to avoid repetitions. Shadows and reflection are also feature of another engine, we cannot port them, of course.
Well the reason for the texture format change is because the game's running on a GPU that accepts a different texture compression format, which, in the iOS version's case, is PVRTC. I don't think that they used a different engine apart from the change of APIs to OpenGL and some platform-specific modifications.