After +35 years in the Hospitality Industry, I would agree Erica's response, and include other factors as well.
Prep times can be different dependent upon:
- efficiency of individual
- efficiency of environment
1) Individual: experience counts, obviously, this is why the "new person" starts in the prep section- peeling potatoes, dicing carrots, cleaning shrimp; with more experience handling the tools of the trade & understanding how to consolidate movements and improve workflow, more intensive and valuable items are added to the Prep List, such as pin-boning fresh fish fillets or dressing game hens;
2) Environment: in food production, as in the production of any other product, an efficient Work Space is of great benefit ( also obvious, once it's put into perspective ); compare your home kitchen to the kitchen of a commercial bakery, for example, with deliberate lay-out of equipment, work spaces, and storage, as well as the division of labor that will dramatically shorten the time to produce 100 apples pies, for instance, with one apple peeler, one apple chopper, four crust makers...
Therefore I would submit that to author a definitive prep time for the myriad of food items currently used in the Restaurant / Hotel / Institutional arena would be foolish, actually, maybe impossible, without taking these two ( and other ) factors into account.
Also, to create and enforce a standardized, or minimum / maximum prep time would actually be harmful. To expect an aspiring chef to be able to clean and prepare 25 whole turkeys for a buffet, within the same time that an able and experienced chef would complete such a task, risks danger to the new-comer by hurried, improper, and unsafe knife handling ( for just one example ). Furthermore it increases the risks to the guests that may consume a contaminated final product, due to the our new-comer attempting to finish this task in the arbitrary allotted time.
( other factors: just gonna put this out there... a large hotel operation, with a prep staff that is in the union, in my experience, will be much slower - or more deliberate, perhaps - that the aspiring sous chef who needs to prepare the dinner special at 4 pm...! )
An efficient operator will calculate these times themselves, and continually review them, to save labor, and increase efficiency.