Voyage is not the only company to use Fusions and Pacificas in its test fleet, which may make the case something of a bellwether.

"We believe there is absolutely no merit to this lawsuit," said Voyage CEO Oliver Cameron.

Cameron, a former vice president of engineering, content and product at Udacity, founded Voyage in 2017. It's one of a number of self-driving startups focused on deploying slow-moving shuttles in niche areas. The company has set itself apart by focusing on retirement communities, bringing new mobility options to retirees. It operates in The Villages, Fla. In December, it announced it had signed a multiyear contract to deploy autonomous ride-hailing services there.

The company uses the Fusion sedans as part of its testing and development process, and the Pacifica minivans are part of its consumer-facing fleet.

"It is somewhat sad, because I've studied Voyage quite a bit, and they're a good company and very friendly from an outsider perspective," Nix said. "But they derive a lot of value out of these cars. If they didn't have prototype development, how much would they be worth? They wouldn't exist without these cars, and when you look at it as a patent owner, hey, you are getting some real value by using my patent."

The lawsuit seeks unspecified damages and "a reasonable royalty." No court date has been set.