Are there any tax credits or something that would make a Mfg want to buy Zero?
No, but they've got a metric assload of very important Intellectual Property in patents, their battery/BMS/motor tech, trade secrets, and experience in what NOT to do making an e-bike. That stuff's important and expensive.
For example, you don't see any diagrams or cutaways of the new motor with the new cooling tech, do you? Or anything beyond vague handwaving explanations.
That's the sort of thing an established ICE company like Honda or Kawasaki would want.
Honda can replicate it all (like they're apparently doing now) or... just buy it by purchasing Zero.
However, then you need to integrate the e-bike technology into a company that's done ICE literally since WW-II and deal with the corporate mentality and way of doing things. Polaris seems to be finding this to be difficult. It looks like Brammo is an indigestible lump so far, seeing as how the new bike is pretty much unchanged.
So there's serious downsides as well as advantages.