Assume Company A and Company B plan on entering into a purchase agreement where A will purchase some of the assets of Company B. Some employees of Company B will become the employees of Company A. Company B has a VEBA to cover the health benefits of its employees. Is it possible to spinoff a portion of the VEBA assets to the new company to fund the health benefits of the newly "acquired" employees of Company B similar to a pension plan spinoff? If so, would those assets have to go into another VEBA?

Yes, and yes. It is possible.
There is no corresponding provision to 414(l), although ERISA fiduciary duties to participants in both plans may impute a similar requirement.
IRS has issued PLRs on similar situations.