Ever since the launch of the official PC version site, there has been a buzz about a line in the features section which suggests that the PC version will give gamers "the opportunity to create their own world within San Andreas." Previously magazines have written that the game will be moddable and have included all kinds of hyperboles to express the possibilities. This led some fans to believe that Rockstar might actually be shipping editing tools with the game, which would allow players to tinker with the data files. Today we can safely confirm that this is not the case.
Earlier this week we contacted a source of ours who thought that "the mod community has learned how Vice worked and things are
kept fairly similar in SA. You should be able to use pretty much the same tools." With the mod tools idea relying on not much more than hope, this answer was rather definitive.
In order to refrain from posting false information, however, we decided to wait for another source on this. Jordan from our partnersite PlanetGTA just contacted me after having a chat with Rockstar's people at E3, and confirmed that there will be no mod tools shipping with the game. Rockstar claims the whole story snowballed from a magazine which happened to misquote them on the issue. In addition to this, Rockstar said that the data files are so similar to the ones of Vice City, that most VC editors will even work with San Andreas.