Are the recommended macronutrient ratios the same for vegetarians, vegans, and people eating meat? Does the fiber content or the nutrient density of plant foods change the recommended calorie intake or macronutrient ratio (carb, protein, fat) required for a vegetarian or vegan diet?
I think there are no studies yet on this topic (if someone finds something I would be happy to read them). Macronutrient needs are simply statistics collected for a big number of people over several years. The real need of macronutrients is different for every person, the tables just show averages based on gender / country / age.
In general, a diet can influence metabolism and hence alter the need for macronutrients, but to find out the degree to which it does so would require a clinical study with thousands of people.
One thing is sure, macronutrients needed depend on weight, so if your diet change your weight, you need a different amount of macronutrients. Does your vegan/vegetarian diet alter your weight? Then the naive answer to your question would be yes (but in reality it is not a good answer).
As a general note, we should also note that each macronutrient can be found in several variants across several foods with some variants being more healty than others. For example, certain fat types are better - nuts, oils - and certain carbohydrates, such as sugar, are really bad.
According only to macronutrient tables, one could simply add as much sugar as they wanted to get their recommended amount of carbohydrates, but that would not be a good choice.
Yes, vegans have the same macronutrient needs as people following traditional diets.
The nitrogen requirement for adults based on high-quality plant food proteins as determined by regression analysis was not significantly different than the requirement based on animal protein or protein from a mixed diet.
In conclusion, available evidence does not support recommending a separate protein requirement for vegetarians who consume complementary mixtures of plant proteins.
Source: Food and Nutrition Board at the Institute of Medicine, Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (2005).