Why couldn't you just save the project with all the correct busing as a template and use that for every new project? You couldn't import them into an existing project but you'd have for every new one?
Ah still doesn't answer your OP. Sorry gt.
HEY gt. Can you drag the entire project with the 2 buses into the project with the 11 buses? Or save a blank template with your 11 buses then drag the project with the 2 buses into that? Edit as needed? You'd still have to re-route your tracks to their proper buses but you'd at least have your audio/MIDI files and the 11 buses ready to assign.