Can anyone comment on what is in store for stationary engines viz. ULSF? From what I know, unless you participate in  an emergency demand response program (EDRP), you're not required to burn ULSF. There are a lot of back-up generators out there that are running on high-sulfur fuel. Granted, they aren't (or shouldn't be) running for extended periods, but every week or month, they're tested. Even if a generator participates in EDRP, it's the operator's responsibility to ensure that ULSF is used. Is anyone enforcing the requirement? It would be great to see all stationary engines required to burn ULSF as well as enforcement of the EDRP rules.
Ultimately ULSF will be all that is available, so over a period of time this higher sulfur fuel will be burned out.  

Most state air pollution agencies are charged with monitoring and regulating this emission source.  The size trigger depends upon a number of factors including the air quality.  And those triggers may vary across a state and through local programs.