I'm in the Ebonheart Pact and here's a general list of what I recall finding in the three zones I've been in. This is on a character with 50 provisioning - although no points are invested into the skill line.

Stonefalls (inc. Bleakrock) - Meal, Drippings, Thin Broth, Snake Slime, Wine Grapes, Snake Slime, Snake Venom, Corn Mash, Dragon's-Tongue Sap

Deshaan - Sujamma Berries, Plump Rodent Toes, Plump Maggots, Milled Flour, Comberries, Broth, Amber Malt.

Shadowfen - Stock, Sifted Flour, Molasses, Spring Essence, Caramalt, Frog Legs, Chaurus Meat, Oat Mash, River Grapes, Suet, Saltrice, Crawdad (in barrels and sacks, etc).

From this observation, I am going to say that the Provisioning item drop tables are related to the zone you are in. If you are in an area that has enemy insurgents, you may very well loot their racial ingredients than that of your own alliances. The additive ingredients that make recipes blue or purple are found almost everywhere with the exception of oats and tomatoes which seem to be obtained through a Provisioning hireling.

If you are seeking specific ingredients, find out what level recipes that ingredient makes and then go to that zone. I'm not sure if you can do this for Veteran rank ingredients, but so far it has worked for me in regards to the sub-50 ingredients.