I think this idea is more applicable to a nutritional concept, the nutritionists are forever debating the benefits of raw food. For diabetics, I think it's more important to get enough of 'the right stuff' rather than if it is raw or not.
For type 1 diabetics, the main thing to focus on is the carbohydrate content. Cooking (regardless of what method) will have no effect on the absolute carbohydrate content of your chosen food. Thus, will not decrease your insulin requirements whether cooked or uncooked. Cooking may alter the way our bodies interact with the carbohydrates; but the carbohydrate content will remain the same.
I have read that the effects of cooking vegetables can impact the absorption rate of the carbohydrate content. It is said this is because cooking breaks down the tough fibrous membranes in the vegetables allowing it to be broken down and processed faster. As a result, the carbs could be converted into glucose and enter your blood stream quicker as there is no fibre to process.
So to answer your question (from my own personal opinion): raw food will not reduce your requirements for insulin, providing that there are sufficient carbs in it. Raw food may have a slower absorption rate than cooked, possibly avoiding excessive BGL spikes which is good.
Grant