The reason I ask if there was a recorded easement on property is that generally property owner has rights of ownership. So the impact of easement on use of property is key. As long as use accommodates easement many uses may be possible unless specifically disallowed.
If width is a few feet greater than car width could we let folks sleep along side of easement with a monitor for cars entering and leaving (ie, do it just for late hours (11–5AM)? Could we run a soup kitchen operation. Could we arch or loft over easement (ie, still accommodating easement). Ownership of property gives lots of possibilities. Not asking you to answer these, but there are legal clinics and student lawyers for whom this would make a great project over a period of time (assuming inevitable litigation). All depends on underlying legal language around restrictions on use.
What is a bit confusing is why the owners don’t purchase the property themselves. Split among units as common property, it would be relatively low cost.
Given property owners want to free ride on the taxes to the City , I think there is a good case here for a more enlightened group to take it over, pay the taxes to the city, and start delivering good use. San Francisco is nothing if not creative in these situations, especially if the rich neighbors haven't done their part.