Drupal Custom Search Results Per Content Type
Here's a sketch of an answer: in a views template for the result set you will have access to the original results in $view->result. If the view is set up for fields output, and includes all the fields required including content type, you can iterate through it 3 times, each time ignoring entries that have the content type you don't want for that case.

It's quite hard to come up with clean-looking code because of the way that views names the field data, but if you don't mind that, you can use the dpm() function of the Devel module to inspect it then code accordingly.