Are there enough other tech companies and startups in San Diego to absorb the workforce? Frankly, a change of firm you’re working for isn’t the end of the world.
This being said, if the majority of the workforce wants to stay in San Diego, they need to show some testicular fortitude and tell management “N-O! And I’m not training a replacement either. If you move, it was nice working for you, but I’m not lifting a pinky to help you.” If they’re faced with losing ~80% of their employees suddenly and having to hire and train a lot of people, they might be forced to reconsider.
BTW – refusal to relocate a significant distance is not grounds for denial of unemployment benefits, either. Unless the job contract required travel, a job 1500 miles away is not considered “suitable work.”