The current restrictions are based on engine manufacturers' guidance which state that aircraft engines should be exposed to a zero rate of volcanic ash. The CAA and other authorities are working with these manufacturers to see whether new evidence and risk assessment can enable safe flight at agreed levels of ash exposure.
CAA update on volcanic ash situation | CAA Newsroom | CAA
Presumably, they can come up with a new set of recommendations on exposure, inspection and maintenance?
Is there a significant increase in transatlantic traffic using the New York/Santa Maria OCAs?