Really? I guess you've never looked at the
GABF style guidelines which is what the pros use in competitions,
The great Micheal Jackon's catalog of beer styles are among the biggest and most respected alongside the BJCP.
There are, as well, a plethora of smaller scale attempts to define styles such as
beertutor.com's style guide,
Hybrid guide based on the BJCP and Brewer's Association like this one from Greatbrewers.com,
ratebeer.com's,
beeradvocate.com's, as well as dozens of others.
Check them all out, they have something in common, sometimes a lot in common, but are never defined as exactly the same for each, with agreed cutoff's for IBU, abv, OG, FG, etc.
So no there is no "official" starting and cutoff points for each style, it's all relative, and very loosely defined, when not using the BJCP like a Bible of commands.