Its not going to happen. They would want to retain quality control and you need to be fairly skilled to make something that looks good in Maya.
Designing a good map is only half the requirement now, making it look good is just as important.
Maya is also expensive, so most of the content out there would be created on illegal software, something which would scare the shit out of any publisher.
It's incredible how long it takes them to release a map. Molten falls is a medium map with no standing out details, they should have relased a doezen of such things by now.
Right now there are like 5 playable maps, 2 of which are dm6 and blood run.