From my very limited understanding of the process, it's simply not something you can apply (for want of a better term) after the vehicle design has been started. You have to start with the homologation requirements and design from there, and even then it's pretty expensive. Both Brammo and Zero did that, as did Energica, where Mission, Lightning and a host of others did not. Without homologation, you can still sell bikes, but they can never be more than "custom" vehicles, essentially built as one-offs, as far as regulatory concerns go.
This has always been one of the reasons Lightning's claim for "fastest production motorcycle" is pretty much BS. Lightning isn't a homologated bike, nor could that bike ever be. No homologation, no production.