There's a hotline they can phone and there's an immediate response. There are provisions in place if they want to switch farms. They just need to go to another farm that has an LMIA in place. They have complete freedom to move around. Granted, that's protecting the Canadian workforce. Currently, the prospective employer would need to have an open LMIA. They would need to have demonstrated that they weren't able to find Canadians.
If they have an open work permit and can go anywhere, they're going to be competing with Canadian citizens for jobs, possibly in sectors they're not required in. Then, there are no fallbacks anymore.