Yes. Assume that your exam has 100 questions. Create the exam and add 15 random questions from the first question bank, 30 from the second, etc. (You can do the math to figure out how many questions from each section, based upon the number of questions that you want in your exam.)
If you want, you can shuffle all the 100 questions. Or if you prefer to keep the question by section, you can create sections in your exam.
If you didn't care which categories the questions came from, you could "indent" the question banks in a major category, then pick 100 random questions from this major category.
Moodle is quite flexible to do what you want to do.